Well, the thing about roses is that a) not all of them are fragrant or flavorful, and b) they are not nectar flowers visited by hummingbirds. I would stick to straight sugar and then maybe hang an additional feeder with something like a honeysuckle syrup. You don't want to go too far outside of what they would find naturally in the wild.
I wanted to keep it simple to start off, and then add more information as we "talked" more about the subject. Also, if a post is too long, people don't always want to take the time to read it.
@claudine, you might want to create a butterfly feeder like this one:
You just put some overripe food in a pan for them, with or without a syrup. Here's the link for the pin:
http://www.pinterest.com/pin/321796335844937387/