Kelly's point is well stated about the focusing on a point in your path. My Sensei has a lovely wife who has just started doing aikido and has had fairly severe dizziness problems with the rolling. Look where you are going, breathe, and if it is still not too helpfull seeming.....dramamine.
After getting used to it, I don't think she is taking dramamine any longer.
Seiza just hurts ..... you get more " stretched" as you go, tho.