Registering a third party SIP number with RingRoost is fairly simple, there are two steps you will need to take. First you need to assign the number to RingRoost (so we know about it) then you need to update your number with your third party carrier to point to RingRoost.
1. Assigning a number to RingRoost
Under the drop down on right side -> Account Settings -> click "Assign a number to RingRoost" -> Call your number and enter to pin to verify.
2.Update your third party carrier number
This exact process depends on your carrier. You will need to point all traffic to your SIP number to:
yourfullnumber@ringroost.com
Note: replace "yourfullnumber" with your number with leading country code: ie:17045851413@ringroost.com
You should then be able to setup the number on your PBX just like any RingRoost number. Note: that your carrier charges will apply as well as RingRoost charges.
Note: See here for using Twilio number with RingRoost:
https://www.ringroost.com/help/topic.php?id=737
