People always have this misconception that if you roll dice you should get a fair spread of numbers and that is just not the way it is. Each roll has the same chance as any other roll to get any number. Just because you roll 1 five times in a row does not change the percentage chance you might roll a 1 again. Now the percentage chance to roll 6 ones in a row is very low, which is where people get confused. Just because the likely hood of hitting 6 ones is low does not change each rolls percentage chance of hitting each number.

I actually have found this game's rolls seem closer to pen and paper rolls than most cRPGs I have played.

You are correct that one can roll 1 five times in a row for example. The original post is flat wrong.

Well, if you roll a physical D20 over 100 times, the mathematical "average"* should be about 10.5, with a deviation of up to +/- 1.5 depending on randomness/luck among 100 rolls. The deviation I just said is not based on science though, but on tests I see online.

I believe the proper term is mid-range (one of the forms of averages in math). For example, the mid-range of a D6 is 3.5.

You can even test it quickly rolling only ten D20. I just did (physical dice) and got an average of 10.7 and then 11.4 (luck). Of course, 10 rolls is very little and could give you on wild average of <5 or 15>.

Note : I am quite convinced that developers can make a pure random generator and that the rolls are truly random in Solasta. Some games have added tricks to modify the average rolls, but say so (like Larian added weighted dice that give a bonus if you roll many low numbers. They did not explain how though.).

@TrickyDickAgain's numbers (i.e. 482 rolls: 39% were a 10 or higher, but excluding all 1s and 20s [?]) do not allow us to calculate the average (in my opinion, except by some vague deductions).