Lay a scaffold board on the extension's roof tiles to spread you weight. The extension roof is at the level of the bedroom windows, so I doubt if you will need ladder (unless you are 5ft tall).
To stop the board slipping on the pitched roof, put a couple of beefy screws in the board and attach some adequate nylon rope. Better still, drill holes in the board.
Haul it up the pitch until it's parallel and a foot or two from the bedroom wall.
Feed these ropes, one through each bedroom window.
Tie the ends to a couple of lengths of timber too wide to pull through the openings and so they are held fast. Wrap something round these to protect your internal decor.
Then step out carefully and sort it out.
Guttering is cheap as chips and use a large trowel to lift tiles so you can see under them to check the felt etc.
Roofing work is pretty easy when you have gained access.
Make sure nobody is below you and breakables are out of the way.
If you are feeling worried about the unlikely event of falling off your shallow pitched roof, tie yourself to one of the internal anchor boards before you step out. Use enough rope to do your work, but keep it short enough to stop you falling off.
Also, move anything below the roof that could do you a nasty if you did fall.
A professional roofer would just step out of the window, no board, no harness, but they are used to chancing it and have the right footwear.