Since the pitching line of a roof must be level, you effectively want a roof that has a pitch that matches the intersection of 2 roofs, matching your two slope amounts. Draw a multi-pitch roof. Modify the pitches of two adjacent sides to have your two slope amounts. Draw a single-pitch roof perpendicular to the intersection of the two sides that you modified.
The Beam tool has a sloped and profile rotation option. Cannot remember if the option was there in AC18 though... Though this would be pitch and roll and you would have less control over the overall shape.
AC18-23 AUS 7000 Self-taught, bend it till it breaks. Win10 | E5620 x 2 | 24GB | K2200