Keep the roadie for sure. I only own a TT bike and no roadie, and have had zero problems with handling, braking, and cornering on my TT bike, even on gnarly mountain roads. Climbing is slightly tougher on a TT bike due to the more aggresive gearing and forward position, but I seem to be able to hang with most racers no problem even on hill climbs. I've now ridden for a fair amount on moderately fast group lines and haven't had any problems with the braking/accelerating to stay on the next guy's wheel, although I'd admit it would get trickier with a REALLY fast group that's doing lots of shifting (25+mph).
I say keep the roadie mainly because there are occasional road packs who may insist you come with a road bike, despite the fact that your higher-end TT bike may in fact brake/corner better than your cheaper roadie, and it's great to have a backup bike or an "experimental" bike where you can throw on/off cheaper parts to experiment, and/or mess around with basic bike repair practice.