(My comment was too long again...) It's good to push yourself a little. Things will always be a little scary. But I did the opposite of what you are doing. I will try anything, without much regard for my safety. I was happily doing standing forward rolls in my 4th class... and then I injured my shoulder later in that same class. Now I'm out for almost 2 months (one already, and one more). So don't be too concerned with rushing things. You might make faster progress by going slowly.

If you don't feel safe doing a technique I think it's perfectly fine to just watch. Say "I don't feel like I know this well enough yet to do it without getting injured." Are you able to learn by watching? Or are you watching to avoid doing the rolls? If you are learning, that's great. If not, ask for the kind of help you need. Someone could work with you. Or maybe you just need time to practice on your own, without pressure to hurry, until you feel like you know it well enough.