How to support a load bearing wall when no temporary wall can be constructed?
If the “old hip roof” sits on a double top plate, you can just support the double top plate with 2x4’s set at an angle from the floor up through the ceiling up to the bottom of the top plate. 

About 8’ of an interior bearing wall supporting an old hip roof does not “carry” that much weight. I’m sure a couple of 2x4 angle braces can TEMPORARILY support the hip roof. 

More important to me is: What do the trimmers sit on? Make sure they are supported all the way down to the foundation.