Role of the Warlock??

Warlock is a team fight controlling hero, he's odd because quite honestly he shouldn't be in a support role, rather boosting his ultimate and farming a refresher, he's a big snowball here, and in the lane you're in, if you're not pushing a tower at lvl 6-7 with your golem you're doing something wrong.

Utilizing powerful combos with warlock and say, magnas or dark seer come to mind.
Generally you want to focus on getting tranquil boots, bottle, point booster early on, finish aghs after you spend the early-mid killing heroes and pushing towers.
Utilize his abilities to cripple lanes, kill heroes, and push the lanes, take away their safe farming areas and continue to pressure them, warlock is an incredibly powerful team fighter and pusher, get force staff or blink dagger for escape or initiation

I don't see how Warlock can fill any other role besides support. Like you said, he is a team fight controller, but his abilities aren't well-suited to any role that requires solo action; that is unless you want to pop your ult in a 1 v 1 fight, which should be saved for team fights. Beyond that, especially during the laning phase, his abilities are tailored to aid your carry, Shadow Word specifically.

I think he is a good counter-pusher, though, as Fatal Bonds helps clear creep waves pretty quickly.