Neat suggestion for a helpful geometry tool, David. That would be fast if it has click-point-hold similar to the Ruler tool of Roll20. In the meantime, there are different workarounds for this. I would suggest the method of making a "Character" named, for example, SPG-15. Set up a token graphic that is a cone of the size & shape for the limited angle of fire. (You can make that graphic and upload, or find it on the web search, or get one from Roll20 Marketplace.... Bonus points if you get a graphic that is a semi-transparent PNG format so the map can be seen through it). Save this token as the Default Token of the Character SPG-15. Optionally give control of this Character to the Player(s) who have that weapon, or just keep control for GM-only. When you need to see this range, drag-and-drop the SPG-15 Character from the Journals tab onto the map; rotate and adjust as needed to show the weapon range. When done, delete the token (you can always get it again by dragging and dropping the Character), or alternately just move all your range-tokens onto the GM layer out-of-the-way. Here is an illustrative example of semi-transparent cone effect shapes on Roll20 Marketplace, though this particular set has a Magic appearance rather than weaponized, this could give you ideas, <a href="https://marketplace.roll20.net/browse/set/301/chao" rel="nofollow">https://marketplace.roll20.net/browse/set/301/chao</a>... Here is a related Suggestion on the forum if you would like to add your comments and vote +1, Area of Effect Templates for Spells