Startle reflex

My boy who is nearly 13 weeks has a very strong startle reflex/Moro reflex. At night we currently put him in a swaddle sack so he can sleep, however, once he starts rolling over I know you can't do that anymore.  Just thinking how on earth he is going to sleep!? Any other people have this issue and any solutions to transition him
Smoothly from a swaddle sack when the time comes!?