He then played a role in Tom Habberfield and Ashley Beck's tries in the first half and Tom Isaacs' after the break before Dan Biggar added a fifth, Dimitri Arhip a sixth and Justin Tipuric a seventh.
Biggar was perfect with the boot, converting five tries and a penalty, while the Dragons had Dan Evans and Toby Faletau tries and nine points from Steffan Jones to show for their efforts.
The win moves reigning RaboDirect PRO12 champions Ospreys up a place from fifth to fourth in the table, leapfrogging Welsh rivals Scarlets who won 24-10 on their travels against Zebre.
Three-and-a-half minutes of constant pressure from Ospreys was rewarded when a quick tap and go from Fotuali'i caught the Dragons cold and he burst through to score.
Biggar kicked an easy conversion in front of the posts to make it 7-0 and was called upon to repeat the trick, this time from the touchline, as Ospreys doubled their advantage.
Scrum-half Fotuali'i started a move that went through five sets of hands with wing Habberfield adding the final touch in the corner with just eight minutes on the clock.
Jones got the Dragons up and running five minutes later with a penalty in front of the posts before narrowly sending a good effort wide shortly after as they grew into the game.
However Ospreys scored their third try of the evening in the 21st minute with Fotuali'i again involved, running the angle before slipping to centre Beck who eased through.
Biggar made it three successful kicks from three with the conversion and then slotted his first penalty on the half-hour mark as Ospreys moved into a 24-3 lead against their Welsh rivals.
The Dragons weren't giving up though as Jones kicked a second penalty of the evening however two minutes after the restart and Ospreys grabbed a fourth try for the bonus point.
After Tipuric pounced on a Dragons turnover, Jonathan Spratt fed Richard Fussell with the full-back breaking clear before offloading to Fotuali'i who passed to Isaacs for the score.
Biggar went five from five with the conversion but the Dragons responded almost immediately with their first try of the match, full-back Evans finishing in the corner.
Jones missed the conversion from a tight angle as the Dragons pulled back to 31-11 but he didn't miss an easy penalty in front of the posts in the 55th minute after Ospreys were caught offside.
He hit the post with another attempt five minutes later before Ospreys grabbed their fifth try as Isaacs and then Fussell broke with Biggar going over.
Biggar maintained his perfect kicking record with the conversion however he couldn't fend off Faletau who picked up a loose ball from a scrum moments later to score.
Evans, overtaking kicking duties with Jones replaced by Hallam Amos, couldn't convert as it stayed 38-19 while Ospreys grabbed a sixth try on 73 minutes, Arhip credited with it as they drove over.
Matthew Morgan, on for Biggar, converted before slipping as he broke away however from that Beck picked out Tipuric in space on the right wing with a fine kick.
He went over in the corner and Morgan neatly converted and, try as they might, the Dragons couldn't have the final say as Ospreys coped with their pressure at the death.
|Ospreys Score Card|
|Newport Gwent Dragons Score Card|