If you get motion sickness easily, then take something. But if not, these rides aren't that bad at all. Rock n Roller Coaster is more intense because of the 0-60mph takeoff and the 3 inversions. If you do get motion sickness, use meds for this ride if you think you'd need it.
Everest has only 1 fairly big drop and it goes backwards for a few seconds. But I don't think it would wreak havoc for a person who gets motion sickness. I could be wrong though.
It also depends on how easily you get sick. Some people are very sensitive and can't do anything. Other's just get aggrivated by certain types of rides, like spinning or high speeds. So use your judgement. You can always ask a CM if you are a little wary of riding a particular ride.