how do i find my roku tvs ip adress without a remote and without it being connected to wifi.

If the TV isn't connected to a network it has no IP address.  You must have a physical remote to connect it to a network unless you can configure a hotspot or your network to match the last network the TV connected to.  You can probably pick up a cheap universal remote that supports Roku TVs at Walmart, Target, Best Buy, etc.

Anything you read about obtaining the IP address from the serial number is nonsense.