| Since you are considering roses and with your other plants I am going to assume it is sunny? I think climbing roses would be really pretty and seems like enough room to me. I was also thinking a mixed shrub border...I was thinking something dense, might stop the "Garbage" Many Herbs are easy to grow and don't like extra amendments. There are so many dif. forms and types. Would you be using the herbs for cooking or maybe as medicinals or potpouri? Maybe you just want to grow herbs for the flowers or scent? Many herbs are nice to be able to just pick a bit of and throw into a tall glass of ice tea or lemonade, while sitting on your front porch! An Herb Garden will take a bit more upkeep to keep it looking nice then a mixed shrub border. You could do taller herbs in the back. Actually if you did a mixture of Lavenders, Rosemary, Sages... that would be a mixture of scent, herbs and shrubs. You could still do a climbing rose as well and with your interest in herbs, might want to look for one that produces lots of hips for making tea. Also you might ask yourself if you sould like to attract birds, Hummers, Butterflys or how much you want to water.
How nice to have a front porch! You could also put a decoritive low fence that would keep the garbage out. As for the leaves..that is free mulch!
Also another option would be Pineapple Guava. I can not give you much details, but had done some reserch and they can be pruned to a shrub shape, produce edible fruit and nice flowers, are not deciduous. I just planted some this year and will see how they go. I always have a hard time getting a finished look and found a great book: California Home Landscaping by Roger Holmes & Lance Walheim it has pictures, descriptions and plant lists for many dif. garden beds... A good herb book is Practical Herb Garden byt Jessica Houdret. If you are near a Borders or Barnes and Nobel, might be worth seeing if they have and take a quick peek. | 
