Dermer's prominent roles encompass lead roles in CBC TV series like "Hi Diddle Day," "Pencil Box," "Guess What?," "Mr. Dress-Up," and others. Additionally, he held lead roles in TVOntario series such as "Readalong," "Two Plus You," "Bookmice," and "Today's Special," among others. In animated series, Dermer has ongoing roles, including characters in "Evergreen Racoons" and the "Care Bears," showcasing his versatility and lasting impact in the entertainment industry.