Enable Remote Desktop Connection on SBS 2011 without need for VPN

I would like to be able to establish a connection from my home PC to my work PC through a Windows Remote Desktop Connection. The server is running on Windows Small Business Server 2011.

A VPN has been set up for me, which allows the RDP to work. However, the company only has three VPN licences at present and thus this represents a limitation.

What would need to be done to allow an RDP connection without VPN? The remote web portal has an SSL certificate.

The previous company I worked for had it set up so that users could log in to https://remote.<<COMPANYNAME>>.domain and see their computer listed, click connect and it would download a .rdp file for them to then log into with their network username and password. I’d like to achieve this.