Ross Barkley, Leighton Baines and skipper Phil Jagielka will be back after their World Cup exploits.
Roberto said: "Mo could be involved on Sunday. He has settled in really well. He and Ross came back at the same time and in different circumstances and for that reason they have created a strong bond straight away.
"Barkley will play a part. He has accumulated over eight hours work on the training pitch now, which is very good.
"He will be part of the team against Porto, not just because it is part of his programme but because it is a day to celebrate Leon Osman's career and Ross wouldn't want to miss that for the world.
"Seamus is recovering well and is on the timescale that we expected. We are not going to risk him on Sunday and we are going to take a little bit longer with that one.
"Luke Garbutt has had a minor, minor problem and should be available for Sunday.
"Rom wants to be at Leon Osman's testimonial on Sunday and he'll be presented to our fans. He doesn't want to miss that occasion.
"But he'll be back in full training on August 7, the same as Kevin Mirallas after their time at the World Cup. We'll then see him back playing in a game before the start of the season."
Tickets are still available and can be purchased online at evertonfc.com or in person by visiting the Park End box office, Everton Two, Liverpool One or the TicketQuarter, located in Queen Square.
Adult tickets are £20 (purchased in advance) or £25 (on matchday). Tickets for over 65's and under 16's are £10.