Tourney is the bottom of the line, basically the same (low) grade of components that you get on bikes from Walley's world and other big-box stores.

The Shimano MTB component hierarchy goes like this (from bottom of the line to top)

Tourney
Altus
Acera
Alivio
Deore
SLX
Deore XT
XTR

IMO you do not want a relatively expensive LBS (Local Bike Shop, name-brand) bike with Tourney components. In that case, if that's what it has, I would just buy it for $150-$200 from the big-box store. The point of a more expensive LBS bike is to get better components and a better initial setup than you do at the big-box store.

The Marlin 5 is a mountain bike (not a hybrid) with bottom of the barrel components, and a more MTB oriented suspension fork that is a lot heavier than the one on the Roam. The Trek site says the Marlin 5 is 32.5lbs which is fully 3 lbs heavier than the Roam. But they are quite different bikes...

The Roam is a fantastic bike, I own a Roam 1, it's the perfect city bike IMO if you ride the kind of mixed terrain that I do - about 1/3 poorly paved roads (lots of potholes and cracks), 1/3 gravel MUP trails, and 1/3 paved MUP trails. The suspension on the Roam performs excellent on this kind of terrain, don't let any naysayer tell you otherwise. But it is NOT a hardcore offroad mountain bike, it's a mixed-use hybrid so used for it's intended purpose it works well and is a great mix of quality, weight and cost.

As others have said though, if you are only going to ride on smooth well paved roads, you may not want the suspension fork, But as I said, if you're going to be riding rough roads and paths, then it works extremely well.

Cheers
TRJB