My 14 month old started having issues at nap time recently. Any tips on how to help him sleep better?

He doesn't fall asleep being rocked or help any more. I've tried, it doesn't work, he wants to roll around before falling asleep. I put him in his crib and he plays for a long time before finally falling asleep. Then he will wake up 1/2 hour later crying, obviously still very tired. I will rock him, and cuddle him then, but he still doesn't sleep. Should I just let him fuss a bit? If so, how long? I know he doesn't have an ear infection or any thing like that because he sleeps really good at night, 12 hours some times waking up once to eat.