(Residental) Rafter to Ridge Condition?
Technically, this is a dormer extension.
His roofs are already at two slopes with the low slope adjacent to the "addition" being a dormer.
In order to make this work, the exterior wall that the new rafters will rest on needs to be extended with a small cripple wall. My fear, and something I can't see from the photo, is that I bet he intends to put a window in this cripple to match the rest of the dormer.
Obviously, the outward forces resultant from the loading on the roof is concerning especially considering the possibility of fenestration.
From a ridge perspective, he hasn't adjusted what was originally in place with exception of the slope. The existing room had collar ties which formed the flat part of the cathedral. I think his intent is to now extend sistered collar ties to pick up the new rafters, which obviously deserves a closer look.
It appears that the framing of the existing roof (and possible ridge) were undersized based on the photo, but that is a whole different issue.