The duo's progression is an illustration of Ryan's vision of developing the club's home-grown players to become the next generation of first-team stars.
Full-back Howard made his Warriors debut in September 2012 as a replacement during an Aviva Premiership clash with Leicester Tigers.
The 20-year-old scored two tries on his full debut as Warriors defeated Bizkaia Gernika in the Amlin Challenge Cup and has gone on to make 14 appearances for the club.
He was called-up to the England Under 20 squad for the winning RBS Six Nations and Junior World Championship squads of 2013.
Centre Stelling enjoyed a dream Warriors debut when he scored a six-minute hat-trick against Bizkaia Gernika in October 2012.
Under Ryan, the 19-year-old has become one of the most talented youngsters at the club. His first try of the 2013/14 season helped Warriors record an LV= Cup victory over Cardiff Blues in November before he caught the eye once again a week later against Leicester Tigers.
Ryan said: "Ben and Max have developed well this season and have grown from their experiences with the first-team.
"I am delighted they have committed to this club and we will support them to make the transition to the next level.
"To ensure the long-term success of this club, it is crucial that academy players have a clear pathway to the first-team and over the next few years we will see a conveyor belt of talent coming through."
Chief Executive Charles Cameron added: "Academy players will play an integral role in the club's long-term plan and it is excellent news to see two talented youngsters rewarded with first-team contracts.
"As we build for the future, there will be opportunities for young players from across the region to follow the same pathway to the top."
Warriors have also boosted their academy with the addition of Christian Scotland-Williamson and Josh McNulty, who will both join the club in the summer.
The forwards have appeared for the Cavaliers this season and Scotland Williamson scored a try on his first-team debut in November's LV= Cup clash with Leicester Tigers.