Rooney, 31, announced on Thursday that he will remain at Old Trafford for the rest of the season after turning down lucrative offers from Chinese Super League clubs.
In response, Mourinho confirmed Rooney would be involved at Wembley for what could prove to be his final appearance at the famous stadium for United.
Rooney has only started three games since before Christmas, all of them in the FA or League Cup, and played just 45 minutes in February, due to injury. Mourinho has not ruled out naming his club captain in his starting line-up although he will not let sentiment cloud his decision.
"I have to make a decision. You know that we normally play two different systems. Sometimes we play with two midfield players and a 'number 10' if you want to call it that.
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"He is an option for me. A final is a special match and he's an option for me."
The absence of in-form Henrikh Mkhitaryan, who picked up an injury in the midweek Europa League victory at Saint Etienne, has improved Rooney's chances of adding to the League Cups he won with United in 2006 and 2010.
And although the Portuguese admits he has not found many players in his career who share his fanatical will to win, a number of United's stars are beginning to impress him in that area.
"There are some. Not all of them," said Mourinho. "I've found people in my career that, in spite of super talented players, (are not) naturally born winners or people ready to fight every day to win, and win and keep winning.
"We all know football is changing. We all know that it is much more difficult than it was before. But last season, a very difficult season for the club and for the players, along with the manager, they managed to win a trophy. It was a good taste for them. So we have to try.