Need help with Swisscom Centro Grande VPN setup

I just moved here from the US. I'm trying to setup a Roku to access US channels, but Roku unfortunately doesn't allow me to configure its DNS settings like AppleTv which means I need to setup a VPN. However, I can't figure out how to setup a VPN on my Swisscom Centro Grande router. The UI doesn't have any settings which would allow it.

I did buy another router which is DD-WRT compatible. However, I can't get it to connect to the internet because Swisscom uses some proprietary coding which requires a Swisscom box to be used as the modem. I can't set my box to bridge mode either because that functionality doesn't exist with the Centro Grande.

So, I'm stuck. I need a solution which either lets me set a Swisscom box into bridge mode or which allows me to set up a VPN on a Swisscom box. I do have Swisscom tv and phone, although I suppose I could go without if truly needed.

Any thoughts would be appreciated.

I did find this which looked helpful:

http://ift.tt/1T0Rx8r

However, my router won't let me upload that old firmware so I can't use the information in the link.

I'm not particularly savvy on router setup so I may be missing something easy too.

Thanks!

Need help with Swisscom Centro Grande VPN setup