@Pepinlady
There should be two cables coming out from the back of the Roku device. One cable is a HDMI cable (for video and audio). Verify that cable is plugged into the HDMI port of your TV.
The other cable is the power cable. Verify that is plugged into the USB port of your TV or into a power adapter at the wall outlet. (may need to just unplug and reseat all the cables).
Assuming the Roku device is working (LED is showing on device), press the Home button on the Roku remote a few times and then maybe look for a physical button on the TV that allows you to switch over to the correct HDMI input for the Roku device. (may be labeled Source or Input on the TV).
Alternatively, on the Spectrum remote, look for a similar button that says Source or Input (or something similar that allows you to toggle between the inputs until the Roku Home Screen shows up).
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102