Plug the cable that comes from the router to the PC into the xbox instead of the PC. If it works, plug the cable you had in the xbox into the port the PC was plugged into to test that cable, if that doesn't work, the cable is bad (same goes for the roku). it could also be those two ports on the router that you had tried connecting to the xbox and roku.
if things aren't working, turn EVERYTHING off, and then just turn on the modem, let it boot for 2 minutes, then the router, give it 2 more minutes, then the xbox, roku, and PC. Check the cable connection on all of those devices.