Without seeing your existing house and the proposed addition it's impossible to give any sort of considered opinion. Can you post drawings of the existing and proposed addition?

In general, one will achieve much greater unity and harmony by maintaining whatever type of roof shape and pitch they may have on the existing house. Of course, the world is full of exceptions to every rule, but if you are in doubt, stay with what you have.

Good luck on your project.

1st. Have you been made aware that changing the size of the window may affect the required light and ventilation for that space, and has that been addressed.
Can you, architecturally, change the direction of the ridge?

The link is to a photo album of renderings I made with software to show the different options. There is also a photo of the back of the house as it is now.

Snoonyb, there are two other windows in the room, so no worries there. And either roof style is feasible architecturally. I hadn't thought about turning the ridge. I will see what it looks like with the computer model.
Thanks

Something about your renderings doesn't match your pictures...
I think you roof on the house part is too tall.

Anyway, I think if you matched the size of window that is next to it, and smaller than your bumpout windows (also not shown in the rendering), it will look okay.
And, I'd probably keep it a hip roof.

Now, as to the pitch.

Your renderings show the roof as if you were 50 feet in the air. You need to see what it will look like from 6' from ground level, since that is where you'll be standing. I suspect you'll be able to go with a lower/lesser pitch on your 1 story addition due to that.

Thank you. My instinct is also to stay with the hip. I will have to lower the pitch and worried it wouldn't look right
. Unfortunately the Software does not allow me to properly size the attic. It's either a 3rd floor or has no height at all. I left it in one of the pictures because I didn't want to erase all the work I did laying out the rooms up there..