Rotate Center

I need to rotate an object around its own center on roScreen, and math is not my strong suit to say the least.
Wondering if someone has an equation to do this. I'm rotating a spiral on top of a stationary circle (you know, like...groovy?) Both graphics are the same size.
I have this so far which rotates the spiral while rotating around the edge of the circle.

'circle and spiral are bitmaps
rotatespy = rotatespy+1

m.screen.drawobject(   x ,   y,  circle)
m.screen.DrawRotatedObject( x+(circlewidth/2), y+(circleheight/2),  rotatespy , spiral, &hFF ) 

Thanks