@Rosier First of all the Roku device has nothing to do with connecting the VCR to the Magnavox TV. If the wire that you using coming from the VCR is connected to a Red, White, and Yellow on the VCR connect the other end to a Red, White, and Yellow on the Magnavox TV. If there is no yellow on the TV connect to the Red, White, and Green. Do not use the orange colored input on the TV.
The Red and White carry the sound so that is connected correctly.