FD not for shifting gears?

That's called an error.

Two chainrings means you have a front derailleur. The LBS person is simply incorrect, or possibly something was missed in the speaking/hearing.

Your bike spec is at https://konaworld.com/rove_al_650.cfm and clearly says "Shimano Claris 8 speed" with 34/50 tooth chainrings.

Find a better shop, or search this site for existing questions/answers that are relevant. Start with https://bicycles.stackexchange.com/search?q=front+derailleur+adjust If none of them match your symptoms, then ask a new question.

They very likely were talking about your front shifter's trim stops.

Your shifter has 3 or 4 positions despite there only being two chainrings. As you shift around in back, the angle that the chain enters the front derailleur changes. This can cause rub. The trim stops exist to change the front derailleur's position enough to eliminate the rub. In other words, when the system is set up correctly, you've got one or two stops in it that shouldn't be moving the chain. (Almost every STI now has 4 but I'm blanking on whether Claris is 3 or 4.)