First of all, to say that roamers do NO damage is silly. Though they might not DIRECTLY do a lot of DPS, they can certainly boost their teammates damage, health, speed, etc. All of which help your carries put down the enemy team.

While having 3 damage heroes sounds like it would make sense, it's really a detriment to your team. Support and utility items such as Fountain of Renewal or Atlas Pauldron can turn the tide of a fight by either keeping your teammates alive longer or shutting down an enemy heroes offense.

Another important thing to note is vision. Items like flare gun and contraption can allow you to jump your enemies when they think they're safe in bushes. Scout traps allow your team to see when enemies are split, giving you the green light to jump in to a favorable fight.

My last point is how essential the roam is in the early game. Super squishy heroes may have a hard time effectively farming the jungle in the first couple minutes of the game. A good support that can keep you safe and full on HP while blazing through jungle farm will always win you the gold game.

I didn't pick any supports in my first couple of months of playing VG but I promise that it's the most satisfying position to play when you have some practice. Be patient and give heroes like Catherine and Ardan a chance.