I'd have to agree with roses. I think I've had up to 25 different varieties growing around my house, just beautiful and some of them smell just incredible!
What's my favorite flower? Whichever one that I can give to the woman I like that will make her light up with a big smile on her face when she receives it.
Tulips, especially yellow ones. They just feel so bright and happy! I also love orchids, and roses particularly for the smell. I found a black-looking orchid once, from a grocery store in Las Vegas of all places. It was gorgeous and I kept it alive through several moves, until it finally died after one particularly stressful trip. I've never found another, which is a pity. I loved that thing!