Thats correct you cannot dial directly from TS. We have some 20 users in morocco who connect to our Cheshire site in the UK using Terminal Services. To do this we have created a VPN connection and connect then using the TS client. The only options available to you are:

Connect using RAS and then connect using your TS client
Create a VPN connection and connect using your TS client
Or use Citrix which has dial up capability

The best option Amanda would be the VPN connection because you are not handling modems on your incoming calls on the server and its distance independant.

Hope this helps.