I just replaced the roof shingles on my work shed. It has a gambrel roof. Where the lower slope meets the upper slope the shingles hang over about 1.5". The suns heat has taken care or the southwest side of the roof and and shingles have folded over and stuck to the tar strip. The northeast side though is blocked by lots of trees and has constant shade. The shingles are still as straight as the day I installed them. I was going to bend them and use roof cement to tack them in place but the first shingle I tried popped back up. I was going to use a heat gun on them but I'm not so sure that's a great idea.
You should have used a sheet metal flashing at that change of pitch location, but since you didn't, a moderate heating with a heat gun, properly paying attention to not over-heating them, would probably do the trick.
On a gambrell a profesional will break up the transition with either a drip edge and or a trim detail.
We like to use PVC composite trim like Aztek or Permatrim with a drip edge and proper overhang.
bending it around is not a good way.