As far as you being afraid of "doing something wrong with her", taking her out to dinner for her birthday isn't a bad gesture. Roses might be a bit too much though if you guys aren't "together".
Chances are you have fallen into the "Just Friends" zone from which there can be no hope. If you guys really are that close of friends, then you shouldn't have any problems with simply talking to her about her feelings for you, or whether or not there are any.
Two things will happen if you do it, however.
1. You find out that she doesn't have "those feelings" for you, and wants to be just friends. Things get "weird" after you talk about it, and your friendship gets "weird".
2. You find out that she likes you too, you guys date, get married in a few years, 2.6 kids, white picket fence, etc....happily ever after...blah blah...
It's up to you as to whether or not you want to risk having things "weird" between the two of you, or just keep it casual as friends.
Personally though, (don't take this the wrong way) but any guy that is finally willing to put the moves on a girl he has known for over 4 years sounds pretty pathetic. Chances are you haven't really dated much (if ever), are a virgin, and have always been considered a "Nice guy" and that's about it. You probably consider yourself a romantic at heart, have a younger brother or sister, and consider yourself closer to your mother than your dad.
Am I close on any of those?
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