Roberts told TMZ he discovered the half dollar-sized growth behind his knee last month. Doctors told him Friday testing on the growth came back positive for cancer.
He said he'll have surgery Tuesday to remove the tumor, which has grown into his muscle.
"If the devil can't defeat me, cancer doesn't stand a chance in hell! Pray for sick children who face this horrible disease 'cause The Snake will be just fine," Roberts said.
Notable deaths of 2014 [PHOTOS]