During our remodel we took the kitchen apart and added a new sub floor to the entire kitchen. We also had the roof raised and replaced above the kitchen. cabinets are in and so is the dishwasher, now I have to put in the plumbing. There is a basement below the kitchen where all of the plumbing is easily accessable. One pipe of the plumbing use to run up the inside of a wall in the kitchen and out the old roof. That wall is no longer there, so putting the pipe where it once was is not an option. Also, because we have a low slope roof, everyone I have talked to has said to avoid putting holes in a low slope roof- this will only lead to trouble.
Here ( finally) is my question:
Do I have to have a pipe that exits the house through the roof, or is there something like a diaphragm I can use to avoid putting a new hole in the roof.
There is a plumbing pipe that exits the house on the opposite end of the house. Can I join the kitchen pipes to the other set of pipes that exit the roof, or do I need to have the 2 vent pipes like I use to have?

Thanks for the help.