Neither player has established himself as a regular since that deadline day deal in August and both are expected to be on the bench tomorrow when Fulham play host to the Royals.
But Coppell would rather have England Under-21 international Rosenior to call upon as Seol, who lives near Fulham's training ground, had engineered the switch in the first place.
He said: "We got the better deal because Seol didn't want to be here.
"He made that clear to everybody here. He wasn't kicking up a stink about the situation but was very quietly, but equally forcibly, saying he preferred to move on.
"He said he wasn't guaranteed first-team football but at the time he was in the first team. There was also New Malden as well, the centre of the Korean community, so from a family point of view he preferred to go."