vpn or another route?

i have a client with a server 2003 r3 w/ roaming user profiles on the server. we need to allow access over the Internet to the server for 2 clients. The server is setup in house using public IP addresses and DHCP. They need to access programs and network resources.
I’ve looked at remote desktop software but they don’t look like they will work to access the server?
Do i need to get IP address from their web-host to configure or can i tunnel without them. I’ve been reading technet.microsoft but I’m confused.