Mark Selby overcame Robertson 10-6 on Sunday to win his third Masters since 2008, but 2010 world champion Robertson feels that the game's leading professionals continue to live in the shadow of the absent O'Sullivan, who has played only one competitive game since lifting his fourth world title with an 18-11 win over Ali Carter last May.
O'Sullivan opted out of this year's Masters for the first time in two decades after announcing in November that he was withdrawing from the rest of the season citing personal reasons amid his well-publicised problems battling depression away from the game.
He turned up at Alexandra Palace looked relaxed and in good spirit to watch some of the play over the weekend as he continues life away from the game.
Two-times world champion Mark Williams has already called for O'Sullivan to return to snooker saying on Twitter last night that O'Sullivan would have won the Masters with some ease.
He has apparently been working on a farm, but has until the end of February to notify World Snooker if he will be returning to defend the title at Sheffield's Crucible Theatre.
"When Ronnie comes back to the World Championship, he is going to have a lot more of fear factor than what he had in the last few years," said Robertson. "The last few years, players have seen him all the time and played against him in matches.
"Now he is going to get that aura back where people are going to twitch against him a lot..that includes a lot of the top eight. If he comes back, he is going to be the favourite I would think.
"He is such a talented player, he doesn't need to keep practicing. As long as he keeps practicing once every couple of weeks, he'll be alright. We'd love to have back, absolutely."
World number one Selby defeated O'Sullivan in winning his second Masters title in 2010, but agreed with Robertson that the game is missing his presence.
"I think it would be good to see Ronnie back," said Selby, who collected £175,000 for usurping Robertson.
"He brings a lot to the game because he is entertaining to watch and is a great player.
"He is one of the all-time greats, and I think it will be a shame if he doesn't come back for the World Championship.
"He is defending champion, and I think it will be nice to see him come back ready for the World Championship to defend his title."