The ovens do not cause the RCD trip because there is nothing wrong with the ovens.
Your fault conditions are unusual - you talk of the RCD trip when you switch the grill OFF - I suspect that this is a typo and that the RCD trips when you turn the grill ON - but no matter.
Either way you need the services of a specialist
It may be as simple as a defective grill element.
Good Luck...
September 2015