Elgin,
Underarmor has a "heat gear" line of products that is probably up your alley.
If you want to rollerblade around without looking like you missed the exit for the Tour De France (or maybe you do... thats cool too
) look into finding a simple Coolmax, or other similarly branded Tshirt. Same thing as a regular Tshirt, except it breathes and wicks away sweat. Should also stay a lot drier than a cotton tee.