The Scotland international claims the on-loan forward would benefit from another year at the Hawthorns and wants the Belgian to stay if the Baggies are to reach the Europa League.
Lukaku is on a season-long loan from parent club Chelsea, with an extension or permanent move yet to be negotiated. The 19-year-old has scored 12 times this season in the Premier League for Steve Clarke's side, and he found the back of the net in his last match against Swansea to take West Brom into seventh place in the table.
Although Lukaku missed a penalty in the same game, he is still the highest scoring teenager in the top five leagues in Europe, and his teammate believes he should stay in the Midlands.
"Will he benefit from another season at West Brom? Definitely. You think how young he is for such a big unit," Morrison told reporters. "He is a pleasure to have and I think he will be even better next season.
"He's got a lot of hard work to go but I'm sure he is going to be a top player. I'm sure Chelsea are going to develop him."
The Belgian has played 19 times at international level, scoring three on three occasions, and Morrison is aware of his qualities and how important he is to the Baggies' push for Europe.
"Romelu's goals are one of the reasons we are where we are. Hopefully the club can get the deal sorted [for next season]," Morrison said. "He is big and strong and scores goals and is quick and powerful. He is a handful for anyone."
"Probably the manager will realise that and hopefully we can get there and build a squad for it."