My daughter is 3 years old. She easily got some sweat in the beginning of her sleep, no matter it is in summer or winter. Then she is fine in the late of night. She started sleep alone since several months. Before that, she also sleep in her own bed within my room.
I usually cover her some thin spread or quit. I checked her twice. Once is around 1 hour after her sleeping. Another is before I go to bed. At the 2nd time, I change her with thick cover.
When she was a baby, I use some small cover. After she is 1.5 years old, I used a normal cover for her. So no matter how she rolls over, she always get something covered. The only issue is that she can't clean up bed after she get up now. She is still too tiny to folder a big quit.
BTW, don't cover kids too much. I cover my daughter as I have or maybe a little less. Also kids really know how to protect themself. e.g. My daughter sleep with face when she feel cold. Sometimes she also called me or her papa to deal with some hot, cold, wet issue.
Just share my experience.