Welcome to the world of vertigo.
For a good write-up on what happens in the inner-ear canals and why you feel off-balance after any type of roll, read Aerobatics; Principles and Practice by David Robson. Particularly chapter 3. But what you describe is entirely normal - I still have the exact same thing despite doing aerobatics regularly for about two years now.
There are four ways in which you can limit the effects:
- Practice, practice, practice. At least one aerobatics flight every two weeks makes you very resistant to the effects of high-g and rolls.
- Make sure you are well prepared and physically fit before flying aerobatics: no alcohol the night before, well rested, well fed, not too much coffee etc.
- Don't do too many rolls after one another. There are various other aerobatics figures that require little or no rolling. Loops, stall turns and cuban eights come to mind. Plan your activities or sequences so that you alternate pitching maneuvers with rolling maneuvers.
- Use proper lookout techniques (for rolls you normally look dead ahead to the "sweet spot" around which the aircraft rotates) and don't move your head while rolling.
But unfortunately rolling is the primary effect of one of the three main flight controls, and a secondary effect of another. So most aerobatics figures have some sort of roll, or rolling effect in them and it's impossible to avoid them altogether.