I have to agree with 4ears that EQs are not the way to go, for a couple of reasons. However, if the room resonance is that bad, then maybe an EQ is the lesser of two evils.
1) An EQ adds alot of circuitry to the audio chain.
2) An EQ lessens the overall output at the room resonance (however, the room resonance is still present), but really messes up the actual FR near field listening response. For instance, suppose we have a resonance of 7db at 100hz. We adjust the EQ so this resonance is lowered to "normal". The actual near field listening experience is down approx -7db at 100hz. If it does seem flat, we are then listening to the reflections of the resonance still present. At higher FR resonances, real problems develop in the midrange.
Again, having said that, it may be more tolerable with this experience than without the EQ. I would prefer to rid of resonances, if possible, through other means.