So, it's pretty helpful to know where these guys are, or at least an idea of where to look!
Here's a link to a post that has Angmar, MM, & Forochell in it: https://www.lotro.com/forums/showthread.php?564326-Today-s-Roving-Threat-Locations&highlight=roving+threat+locations
Rohan :
The Havens of Belfast 71.6s, 61.2w
NanGurth 5.6n, 23.4w
please post any you come across & I'll keep this top one updated for easier refrence