Goal revealed in early May that the 32-year-old had opened talks regarding a possible switch to the United States.
At that time, Rooney was said to be frustrated with life at Goodison Park under Sam Allardyce.
Allardyce has since been relieved of his managerial duties with the Toffees, but Rooney is still holding transfer discussions and D.C. United boss Olsen remains optimistic regarding his chances of landing a high-profile signing.
He told reporters after a 1-1 draw with LAFA in Los Angeles on Saturday: "There is interest in Wayne Rooney from our end and I think there is interest from his end too.
"I hope it can get over the line because he's a very good player who can help us. He would be a great player for this league.''
It has been suggested that personal terms have already been thrashed out with Rooney, with all parties now waiting on the green light from talks between Everton and D.C. United.
Olsen insists no agreement is done as yet, but the ex-England captain and his representatives have been in America of late and a switch does appear to be close.
Olsen, who spent 11 years with D.C. United as a player – with that spell only broken up by a short loan stint at Nottingham Forest – added: "Nothing is done, so I don't want to get into talk of arrival until he actually arrives.
"Nothing is ever done in this world and when you're looking at a deal of this scope and size. We'll see, but hopefully we can get it done.''
Rooney only returned to boyhood club Everton in the summer of 2017 following a record-breaking 13-year spell at Manchester United.
He managed 11 goals in 40 appearances for the Toffees, but ended the season with a niggling knock and out of favour under Allardyce.