I can't say if it is the same with roasty as I don't use it much. But I know Labia Majora on Golden Palace is colored via a shell for the Majora which was added through Pussy Wizard. So I'm not sure if roasty has a similar shell or not.
I'm not sure what is going on in your images though, it looks like it could be a shader mismatch/application error or even a case where the Applied character Materials are using a non-standard UV.
Also make sure you are applying presets to the right figure, ie MAT Copy should be applied with base figure selected, presets you'll usually either have graft or shells selected. Though Meipe has started using H. Materials more which allow the base figure to be selected and it will apply to the graft or shells, however not knowing what changes az has made with the Alpha, they may have broken/changed H.Material implementation in 2025 for all I know. I mean I know the 2025 script was needed because Daz changed scripting enough that previous versions scripts no longer worked, so perhaps they've changed how H.Materials are working.
You can always try copying the body material from Genesis 9 manually if the scripts aren't working. Go to Surfaces select Body, Right Click and press copy, then go to Surfaces on Roasty pick Body, Right Click and Paste. As long as the shaders are the same it should copy the G9 Body surface to the Roasty Body surface.
Really with it being in the Alpha though there is so much that Daz could have changed, that is going to break how products might work.