The minimum roof slope for metal roof panels depend on 3 different scenarios.
Roof slope fire egress.
Most states and townships have building codes that require means of egress on each floor sometimes including finished basements and attics.
I interpret this to mean that if the door is locked on the stair side preventing free access to the roof it does not need to provide free egress from the roof.
Paragraph 7 2 1 5 8 9 from nfpa 101 says that roof doors have to either allow free egress from the roof or be kept locked.
Lapped nonsoldered seam metal roofs without applied lap sealant must have a minimum roof slope of 3 12 25 slope.
For example a fire escape is defined as a means of egress because it s a way for someone to exit a building in an emergency.
The occupant load number of dwelling units and common path of egress travel distance do not exceed the values in table 1006 3 2 1 or 1006 3 2 2.
Emergency exits on these floors usually come in the form of egress windows.
This means for every 12 horizontal units the roof must rise a minimum of 3 vertical units.
A single exit or access to a single exit shall be permitted from any story or occupied roof where one of the following conditions exists.