The Belgium international forward was a huge hit while on loan at Goodison Park last season and the Toffees boss is keen to sign him permanently, with a deal close.
The Toffees are close to agreeing a deal with the Blues to bring in the Belgium international for around 22 million euros after his successful loan spell last season.
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"Rom fits in really, really well at Goodison," Martinez told talkSPORT. "We created a fantastic bond with the player, and the player with the fans, and that is something that we would love to extend.
"It is difficult to say because he is not our player and I would never be disrespectful in that respect. He enjoyed his time at Everton, he developed as a footballer and we hope the parent club, Chelsea, were very happy with that loan relationship.
"Whatever happens in the future, at the moment there is not much we can speak about."
Martinez did, however, declare himself confident that "a few" reinforcements would be secured before the end of July, having already recruited Gareth Barry from Manchester City on a permanent deal and confirmed that a move for forward David Henen is close.
The Spaniard explained: "The main priority was to have continuity in what we did last season. We have had a few players signing extensions and we got Gareth Barry becoming a permanent signing, which was huge for us.
"In the next couple of days we will have a few players coming in because it was important for me to assess the youngsters. The youngsters have done terrific and are showing the good work we are doing in the academy at Finch Farm but there are areas that need to be strengthened and, over the next few days, we are going to get the three, four players we need just to finalize the squad facing the huge demands with European football ahead of us."