In Tinto (and I think any Paradox studio, though I might be wrong) we don't have anyone whose sole task is historical research, but historical research is an important skill that we look for in almost every role.
This is expecially true for what we call "content designers". They are typically the ones who are expected to do the most historical research for things like events, missions, or the country setup. However such people also need good game design skills to turn that research into fun gameplay, and good technical skills to script it into the game.
Every role does some research though: artists need to know which hats to draw for X culture in Y era (and if they had beards), programmers need to know if their improvements to the system they are implementing makes historical sense, leadership needs to direct the games on a path that feels historical.
So, while we are unlikely to need a pure historian at Tinto, it is something that would help your application for other roles.