When you say rotate what exactly you mean; simply rotating unconstrained parts OR rotating in an animation.
These parts are mated in a upsidedown position. I need to unfix the parts, rotate the parts, 180 degrees around and then re-mate to the surface.
I assume when you use the triad manipulator, you, rotate a part on its centre or gravity?
I would like to: float the 5 parts, select them together and roatate them on their own centre of gravity at the same time, then select the surfaces to mate again.
When i try rotate them all selected, they seem to rotate on the combined centre of gravity.
This is simply to suggestion to rotate them all at the same time, instead of individually
Hope this helps
If I am understanding you correctly, you should try flipping your mate alignments on the current parts until you get the desired orientation. This should save you a lot of time deleting mates to just rotate and re-mate. As far as the original question, I do not beleive there is a way to rotate individual parts about their own axis if multiple parts are selected.
Brian's solution is correct to fix your current issue,
Just so you know there is a Viewer rotation which is your middle mouse button. Then there is the Move\Rotate of an assembly component. If your parts where free and had no mates attached to them you can pre-select each component, then select Rotate component and all your parts would rotate.
The option of to Rotate around XYZ axes did not work in connection to components' axes. Therefore I made it the other way.
Quickly bring a instance of the component from design tree (Ctrl+drag).
Mate it to existing instance and set so it is upside down.
Fix new instance of component.
Delete old instance.
Mate new instance if required.