England only held a 10-5 half-time lead at Stadio Olimpico, but stepped it up after the break to move four points clear of Ireland at the top of the table.
Youngs opened the scoring with an early try and Owen Farrell added a penalty, but rusty England – playing its first game since the tournament was suspended in March because of coronavirus – was pegged back by a Jake Polledri five-pointer.
Scrum half Youngs added a classy second two minutes into the second half before Jamie George marked his 50th cap with a third try and Tom Curry secured the bonus point 14 minutes from time.
Henry Slade scored England's fifth try and Farrell kicked nine points as England boosted its points difference and consigned Italy to a 27th consecutive Six Nations loss.
Youngs got England off to a great start when he cruised under the posts four minutes in after taking a pass from Farrell, who added the extras and slotted over a penalty soon after.
Italy hit back, though, with Polledri bursting from midfield and finishing superbly in the corner after showing a sharp turn of speed midway through the first half.
The fired-up Azzurri applied the pressure after Red Rose debutant Jonny Hill was sent to the sin bin for a high tackle, but were unable to capitalise on their numerical advantage and England was frustrated when it was penalised as it drove towards the line after a yellow card for Polledri.
England failed to fire in the first half, but Youngs caught Italy out again with a moment of magic just after the interval, throwing a clever dummy at the breakdown and shrugging off a tackle before dotting down for a double.
George applied the finish when Italy was unable to stop a driving maul after a lineout and Curry showed great awareness to dart down the left touchline and touch down for the bonus point.
Ben Earl set up Slade for a simple score after getting on the end of Farrell's grubber kick as Italy ran out of steam and England piled the pressure on Ireland and France.