There's no problem having them both installed. Just don't start either of them automatically on startup and you'll be fine (they aren't configured to be started automatically by default, if they do, it's something you've configured yourself and should know how to disable).
My bet is also that maybe your router did remember the old IP when using DHCP... I rarely use DHCP so I don't know if that's common or not, but most likely scenery IMHO.
I have several TCP/IP stacks installed on my systems, and only thing you need to notice, is that Roadshow has bsdsocket.library as a file while others create it dynamically to memory. So, if you plan to have Roadshow and any other stack installed, remember to rename the file out of use when starting another stack and back in use when using Roadshow.
