Sorry for the delay in response.
Yes, and no. Sometimes I work out the fingerings exactly and play it the same way every time. Other times I can do it on the fly without figuring out the exact fingering.
My thought process here was this:
We need to play that 9th fret on the 3rd string started in measure 4. That’s my target melody note I’m looking to hit.
I want to hit that note with my thumb so it has power and stands out.
So I kind of reverse engineered it from there. The previous index finger at the end of measure three is basically just filler.
That T, I, M, I roll is very common though and one you’ll want to master.
If you know the most common Scruggs lick it uses this exact roll in the middle of it.