I don't know about the rosemary and lavender, but I over wintered chocolate mint in an 8" pot. It wasn't pretty, but I put it outside in spring and it is flourishing. My chives and thyme survived outside in large cinder blocks close to the building, but they also had a good layer of snow for insulation. My Greek oregano, planted in a hollowed out section of log did not survive, nor did my sage, planted similarly. They would have made it in the ground or a raised bed. I don't have a garage(apartment dweller), so if I don't have room for a small pot of something inside, it's got to take it's chances outside. I think your garage would be a perfect place for overwintering, as it would still be warmer than outside, being attached. I would take some cuttings also of the rosemary and lavenders to put in small pots as a back-up. If everything survives in the garage, you'll have extra plants.

Keep in mind that over time the rosemary will become a very large shrub - unless you are willing to replace it every few years or so I wouldn't plant it in a pot (unless it is VERY large pot). Or does it grow slowly in your region? Lavender needs a lot of sun and warmth - I am not sure it would overwinter inside well. No harm in trying, though! :) My mother left a very healthy spearmint plant growing by her compost pile out every winter and it always came back! (She even mowed in every once in a while and it survived like that for years) I think the mint overwinters just fine. Good luck!

Yes, Sheila is right...mints can survive frigid winters. I had to over winter mine indoors because it was in a pot and I didn't have a place to plant it in ground. Sorry, I didn't mention that. I'd tried a previous year to leave one out in a box, but it didn't survive. Pots and most other containers that aren't open to the ground just don't have enough insulation from the below freezing temps our zones get in the winter.

"Lavender needs a lot of sun and warmth - I am not sure it would overwinter inside well."

In my case, I don't expect the plants I over winter inside to do great, but just survive, so I don't have to purchase new plants or start from seed in the spring. Some of them surprise me and make decent looking houseplants for the winter(scented geraniums and fibrous begonias for instance), others look pathetic but survive(like my mint).

FF, if you have enough room under lights for some small lavender plants, they may do well. I have started lavender from seed before and kept them under flo lights for several weeks before planting out and they were only several inches tall, but very healthy.
In any case, I think your garage would be cold enough to allow your plants to go dormant, yet warm enough to keep them alive, especially if you could place them near the adjoining wall to your home.
And Sheila, I do envy your gardening zone!