Remote batteries have been changed, remote works on/off and volume but when I hit the home button; it will not go off screensaver to home or if push back button won’t move either. At this stage voice command does not work either. How do I fix it?
Sounds like you have a Voice Remote.
The TV controls (power, volume, mute) control the TV via infrared (IR). Since these controls work, you remote is still correctly set up for your TV brand.
The Roku controls (everything else) control the Roku via WiFi. For this to work, your remote must be paired with the Roku it is to control. If not paired, you won't be able to issue any commands to the Roku, like to exit the screen saver. It sounds like the Roku has lost its pairing and needs to be re-paired to the Roku.
Remove the remote's batteries, pull the power to the Roku for a few seconds, then plug it back in and wait for it to start up. When it's started up reinsert the batteries in the remote and press the remote's pairing button.
If your remote is a newer one that does not have a pairing button, press and hold both the BACK and HOME buttons near the top of the remote for 5 seconds or more.
Reference: https://support.roku.com/article/360011621473
Video from Roku re how to pair point-anywhere remote:
https://www.youtube.com/watch?v=EK3T6eXqPU8