It's fairly rare for a roll to contain both cooked and raw fish, isn't it? (That's just my impression, maybe I'm wrong! It usually seems to be one or the other.) Even if you did consume a tiny amount of raw fish, chances are very high that it won't harm you. You probably don't want to be eating sashimi every day, but once is statistically unlikely to cause any damage. In plenty of cultures raw fish is more common than in the U.S. and I don't think it has a negative affect on pregnancy.