Can you add Wool Roving to your wool project?
I love working with wool roving. I do add that to work that I have done but not often because you have to FELT it into the base fabric using a felting pen. That's a barbed tool usually having 3 barbed needles or more. Clover makes and sells this product. It is great for using when you want to "paint" on the wool since roving comes in all kinds of colors.
When I do the felting on wool you are so right, it can make it unstable. I honestly don't remember what the heck I did when I was doing felting on wool but I probably used a stabilizer underneath it.
And I do like to use flannel to back my work but I have used cotton as well. It depends on how you are going to use it. If it is a really heavy piece that you want to hang, I would recommend the cotton. Flannel has more movement to it so it will sort of drip if you know what I mean. Lose it's shape over time because the weight will pull it down.
When I did My Blue Heaven I actually used a fusible in between the backing and the top. Then I pressed it with a steam iron from the back so it would bond. It prevented it from drooping.
Hope this helps if you are having any questions about how to finish your wool project. There may be better ways to do the finishing but I did mine this way. It was pretty simple and because the project was pretty heavy, I am glad I did the fusing. Probably would not recommend fusing it if you are planning a project that is going to lay flat, like a table runner.