It is very difficult to grow things under pine trees.

Here are some suggestions.

http://www.seedsofknowledge.com/pines.html

Forget-me-nots are basically a wild flower. They bloom mostly in spring, and require alot of moisture.
I have success under oaks, with Lily of the Valley,
spring bulbs, and ivy. Ferns are nice too.

Wild type plants do better in difficult situations like you have.
Making sure there is enough nitrogen in the soil, is also important, as trees drain it out. Same with water.

I don't think roses would work...they need alot of sun.
But you might get some daylilies to bloom there (if you get 1/2 day sun at least) and there are some nice little types that are yellow.