Kibbee's suggestion is a good one. You should feel comfortable on a fast group ride...one that has a pace range of 35-40 kph. YOu should also be able to handle surges in speed and intervals of speeding up and slowing down. You should feel comfortable in a group of riders. I'm not just talking about being able to ride in a paceline, but also feel comfortable with 5-10 riders in close proximity to you - elbows almost touching, handling corners, etc. Find a moderate roadie group ride and go out with them a few times, you'll soon find if you are cut out for racing or if you need a little practice. Talk with the guys/ladies on the ride and learn all you can. Experience is invaluable.
Fitness is definitely important, but handling skills are often overlooked with new racers. It's both for your safety and the safety of others that you are able to hold a line, know pack etiquette, and are not going to be jumpy or make lots of wild riding or erratic moves.
A common issue with riders coming from the TT world is just that. They are fit enough, but they are used to riding by themselves and not necessarily drafting or riding with several people around them.