You created a segmented roof with the "drawing an arc and then extruding" method?
When working in this manner, you shoudl have "AutoGroup" active to group the segments.
Also, you should not "Suspend Groups" to over-ride that grouping protection.
If i was you and had allowed roof segments to drift apart, I would simply rebuild the roof and not bother to re-assemble the bits and pieces.
Further: the segmented roof method is obsolete considering what can be achieved with the complex profile as a wall.
Dwight Atkinson