POCO's here determine that.
Last support is 30 or 36" from top of weatherhead. Mast brace if eaves, 3/8" thru bolted if unistrut or 2 hole strap.
Riser over 36" must be back braced with 2, 3/4 emt feild built braces attaching to the point of attachment and thru bolted through a rafter.
No point of attachments over 6' above roof (new rule)