Kroell was born in Chicago, Illinois, and attended Niles North High School in Skokie. There, he became interested in theater. After a break, he attended Harper College, earning his associate degree in political science. Kroell appeared on season one of Bravo's Make Me a Supermodel. In the show, Ronnie entered into a notable bromance with fellow contestant Ben DiChiara, which was dubbed "Bronnie". He became very popular on the show and won the title of "Fan Favorite" despite placing second behind Holly Kiser.