Rossiter is a product of the Liverpool youth system. He is very highly rated at Kirkby and made his debut for the Under 18s as a 70th minute substitute in the 4-3 defeat to West Brom on 24 March 2012- his 15th birthday. Still aged just 15, Reserves coach Alex Inglethorpe called Rossiter up to the Under 19s side for the NextGen Series tie against holders Inter Milan on 8 January 2013. With Liverpool 4-1 up, Rossiter entered the action as a last-minute substitute, and almost slipped Samed Yesil through on goal with one of his first touches- though Yesil was called offside. Upon Rossiter's entry into the match, Liverpool legend Robbie Fowler tweeted "A young lad just about to come on for a few mins for Liverpool in nextgen... Jordan Rossiter, big shout but potentially a young Stevie g.." Rossiter went on to feature quite prominently for the U18s during their 2012-13 season, racking up a total of 15 appearances, even taking the captain's armband for a number of games. His performances garnered much praise and he became recognised as one of the Academy's most exciting talents.
Rossiter entered the 2013-14 season as a more permanent fixture of the U21 side. After several impressive performances, Rossiter netted his first goal for the U21s on 4 November 2013, slotting in a pull-back from Jordon Ibe in the box against Middlesbrough. Rossiter was rewarded for his progress with a place on the substitute's bench for the Liverpool first team's away tie to Chelsea on 29 December 2013. He finished the season with three goals in 19 appearances for the U21s, earning many plaudits along the way. On 6 May 2014, Rossiter was presented with the Liverpool Academy Player of the Season award at the club's prize-giving ceremony.
After competing for the first team in their 2014-15 pre-season schedule, Rossiter was handed his competitive senior debut on 23 September 2014 in Liverpool's League Cup clash with Middlesbrough at Anfield. In just the tenth minute of the match, he netted the opening goal of the game- collecting a rebound of a blocked shot and placing a long range effort into the far corner of the net. Rossiter became the second youngest goalscorer in Liverpool history, behind only Michael Owen.