Hi Walt,
Thanks for the great question. You can definitely use RingRoost for fax. In fact, we suggest getting a number dedicated for fax (versus using a number for both voice and fax).The system to pauses for about a second to detect if the call is a voice call or fax, causing a slight delay in voice calls, so it's generally better to have a number that's just for fax (if that's what you're using it for).
Check out our User Manual's section on the Answer Fax control for more information on how to use this feature:
https://www.ringroost.com/user-manual.php#answer-fax-control
Thanks,
RingRoost Support Team