Easiest thing to do is go into your router and configure it to use your old network name and password.
You can also do the same thing by using a hotspot (again, rename the hotspot connection to use the old network name and password) and then "steer" it over to your new network.
However, you really will want a physical remote in case you ever have to factory reset your device or if you plan on traveling. You can get a replacement remote at Walmart, Best Buy, target, etc.
Note: Do not factory reset a Roku device or RokuTV unless you have a working physical Roku remote (or at least a Roku compatible universal streaming remote).
Also note, there are different types of Roku remotes. Make sure you get one that will work with your Roku.
For Roku TV (one with Roku functions built in) it can use:
For Roku device attached to your TV (except for Roku Streaming Sticks) it can use:
For Roku Streaming Stick, one of the Roku Voice Remotes are all that can be used.