Outward thrust is almost always an issue in a pitched roof, unless the ridge is fully supporting the rafters (load transferred vertically down to the foundation). If any of this is unfamiliar territory, I STRONGLY suggest you consult someone such as an engineer regarding the details before you get too far into it. So far, your posts have not provided an adequate picture of your roof design ideas. You should get the mechanics squared away first. The options for attaching to an ICF wall are many but the design of the roof system has to come first. Good luck.
