How do I "rotate" a rotator?

Apologies if this question is dumb, learning how to work with rotators.

I’m using rotators to tilt a level, using setWorldRotation. Ive got it working fine, but now I need to compensate for camera direction.

Lets say I have a rotator with a pitch forward of 50 degrees, and another rotator with a yaw of 30. I want to rotate the first rotator by the second one, so that the final rotator would tilt the level 50 degrees in the direction of the yaw. How would I do that? Trig?