As far as room acoustics go, you're kind of out of luck. You can compensate for how your sound changes by being in a big room via EQ changes, etc., but there really isn't anything you can do about things like room echo short of physically applying sound absorbent panels on the wall of the room you're playing in.
Besides some minor tonal effects, all a compressor does is smooth out the dynamics of your playing to give you a more even volume, or at extreme settings can be used as a limiter to protect your power amp from clipping if you are really trying to squeeze as much power out of your amp as possible.