Use a roofing mastic to seal the edge of the roof vent flashing shroud to the roof sheathing under the shingles.

If you take the project on I would use a hard board you can go to their site and they will tell you what size to use and how to install, all so on the mastic  are thin set they have the # on the back and what type of spaces trowel to use look at a few youtube clips on go for it best of luck.

Siding, roofing, 9x9 vct, mastic, duct insulation tape, building insulation (vermiculite) to name  a few common ones. 

But these employees can walk, chew gum, and work with my customers!!!!

Regular mastic and grout is easy for something that small.

So, I pulled the trigger...whether it hits anything or not is completely up in the air tonight...but I have a profound dislike of cowards, so by gum, I ain't gonna be one!

There are a couple items that although wouldn't likely completely gum up the financing process, might give a buyer with a bank/appraisal/etc some leverage that we wouldn't prefer they have!  

What I'd think about doing is to make up my patch in 1/2 in. cement board, get me some mastic, and tile the cement board in white, bisque, bone wall tile (whatever color best approximates the fixtures), including the edge with bullnose overunning the edge of the cement board by 1/2 in. or thereabouts.Drill out holes for your plumbing in that tiled board.

@Tyler Gums Before you jump the gun on anything, explain to BP what wholesaling is and the step-by-step process to it.

You can walk and chew gum at the same time.