Hi- the first bloom on a rose seedling can happen when they are very small and just a few weeks old. Or, if they are a non-reblooming type, it may not happen until they are three years old. Regardless, many people sow the seeds in flats and then when they have a couple of sets of real leaves, prick them out into a styrofoam cup full of soil, or something of a comparable size. You can then graduate them up into larger pots as needed for their first couple of years.
I had a few last year that I planted in the ground when they were just a few inches high. Some of them just disappeared, and others did very well.
Yes, you do need to protect seeds from mice and birds, and seedlings from rabbits, deer and mice.

So a 4" wide by 5 3/4" tall pot should be plenty large to keep them in until I can plant them? Thanks for the info, it's very helpful! Now to come up with a cheap plan to keep rabbits and deer out...
Are seedlings generally safe from mice once they're 1-2" tall?

That's going to depend upon how many seedlings there are per pot and of what type. If you have three or four minis in a small pot like that and can both keep them from frying in too high heat and well watered, they could exist their first year or so in many instances. If you've raised seedlings of large climbers or shrubs, one would outgrow that size pot in a very short time.

I created 2' X 4' x 8" deep wooden table planters with screen and wire bottoms which stand on saw horses. I plant all the seeds in them and leave them from planting (around Thanksgiving) until the following Thanksgiving when the temps are cool enough for transplanting and the rains SHOULD begin.

I cover the tops of the tables with wooden lids which are 1" X 2" frames with hardware cloth stapled to them so air, light and water can easily get in, but rodents and birds are kept out. Once they are transplanted, they can go into anything from a four inch pot to a five gallon, depending upon the seedling. I had many fit the four inch pots this year with just as many demanding gallons, two and three gallons and several which required five gallon nursery cans. If the seedlings don't out grow the size pots you've used, they can remain in them until they do. Many seedlings won't generate vigorous root systems on their own and those are often not healthy nor vigorous enough to retain.

Generally, mice, birds, rats and squirrels LOVE the seeds. Squirrels and other rodents will eat the hips and seeds like candy as they've very nutritious and require virtually no effort to "harvest". Seedlings are susceptible to rabbits, rats and squirrels. Keeping all of them out is a constant battle. For the smaller ones, I place them up in a raised terrace where the rabbits generally can't get in to. I have to use traps for the rats/mice. Squirrels are impossible as it's illegal here to do anything to them. For the larger cans, I put the gallons inside and surround them with the larger cans to create a barrier which works to a point. But, as with burglers, if one WANTS in, you can't stop them. Good luck! Kim

That's a lot to think about. I was hoping to plant the seedlings directly from the pots to the soil. I want to try to keep this cheap enough it's enjoyable, so one size pot = cheaper to purchase and keep. What I'm thinking of doing is make two raised beds of about 10" high and 2 1/2' x 8' then put about 2" of sand in the bottom followed by the pots of seeds (one seed per pot; I don't want minis). I was thinking I could make a framed screen (like what you described) to keep out rodents and birds for a short time, but I don't want my roses to be blocked by it so I can't really protect them when they're over 2" high. 1/4" Hardware cloth is too expensive to build an entire fence from it. I can put rabbit fence around the beds and in a year I can probably put in some kind of deer fence, but it certainly wouldn't be 8'-10' high. Luckily we don't have squirrel problems.

Hi- if you want to keep things simple, you might grow them in pots until they reach a size where you can look at them and say, "If this were a perennial from the store, it would have a decent chance in my garden." In my climate, that is roughly the middle of their first season.

Then just plant them out, as you would any large perennial or small shrub. Coddle them (extra water and general care) as you would any perennial through its first season.

As Kim says above, some seedlings will have poor roots and probably won't make it. Others will do fine. The rodents may get a few, and that is certainly annoying. But the good thing about raising plants from seed is there's always more where they came from.

I'll do my best to protect them without fretting, then. After all, hobbies are supposed to relieve stress not cause it :).

I have managed to propagate 3 cuttings of a rosacea "Perfume Delite". They are about 1year old and are single thin canes about 14" tall. As it is spring here they have many eye-buds on the canes, but no leaves as yet.
I am new to rose gardening, but I know that grafted roses have several canes off the root stock. Can I mimic this multicane presentation by planting my 3 canes in the same big pot?
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I've found it depends on the rose. I've had seedlings big enough to plant within a year or two and others that are three years old and still in one gallon pots. There's no way to predict it. You just have to wait and see. I would never put anything in the ground that wasn't at least a couple of feet tall around here or I might as well just invite the rabbits for tea. Besides that I've been known to step on anything smaller, lol! I do have a couple of seedlings of the bourbon Madame Isaac Pereire from 2006 that have been planted in the ground since 2009 that are 6 feet tall and 4 feet wide. So depending on the variety of the parent they could get quite large. Even there though it just depends on what genes the rose got from the parents.

Lin, Perfume Delight is a full size hybrid tea. If you plant all 3 in one pot it will out grow it quickly, especially in your warm zone and long growing season. All own root cuttings start out with a single cane but with time and maturity they will send up more canes as well as branch out from the existing canes. It will probably take at least 5 years for that own root cutting to become a mature plant so be patient.

I've decided not to put them in pots, as I couldn't figure out how to water them. I'm going to plant them in a raised bed and will allocate a 4" square for each of them then plant them in the ground when they outgrow it. If that doesn't work I'll just have to figure something else out! Thank you everyone for the information; it really helped!