What scale and key

When I’m playing licks I like how do I know what scale and key it is coming from when a lot of times those licks do not start on the root note. For example- the supernatural by Gary Moore. I love the song and know how to play it but my assumption is always a pentatonic scale in the key of the 6th string root on whatever fret my first finger starts the licks on. (Basically how can I find the scale without starting of a root or 6th string root?)

It sounds like you are familiar with the main pentatonic pattern, or "box".  The next helpful step is to learn the scale degrees in that pattern.  Because that will in turn help you understand how to play the pentatonic patterns (and eventually other scales) around the fretboard confidently.  You will be looking for root notes and scale degrees across the fretboard and not only stuck with knowing only one root location on the low E string.

This tutorial will show you all the pentatonic boxes.  What shapes they for and more importantly why they have those shapes: it's the scale degrees.  Also important is I have diagrams that show the scale degrees in the patterns.

https://www.guitartricks.com/tutorial/296

For example just taking one simple lick and moving it around will show you how valuable it is to understand and being able to visualize scale degrees.

https://www.guitartricks.com/tutorial/2345/

Hope that helps.

Definitely! What key would you say the supernatural by Peter green/ Gary Moore is in?

D minor.  Both use primarily the D minor pentatonic scale in various fretboard patterns on that whole tune.  They will occasionally add notes from D minor diatonic natural minor.  But the vast majority of the playing in from D minor pentatonic.

The tutorial I linked explains how you get from diatonic natural major or minor to pentatonic major or minor.  The pentatonic scales are just simplified subsets of the diatonic scales.