Are you still using SU2014 as your profile indicates?
It might be that there's an extension that could model a roof such as you are after but it isn't difficult to do it with native tools. You can establish the slopes using the Protractor tool to place guidelines. Instead of typing the angle, type 12:12 and 5:12. I did that here.
Screenshot - 4_10_2021 , 7_40_11 AM.png
Screenshot - 4_10_2021 , 7_49_05 AM.png
FWIW I just used an existing model of a shed that I built. Didn't bother to change the height of a wall as you'd typically have with a saltbox roof.