The midfielder spent the final five months of the season at New York Stadium from Middlesbrough and played an influential role in the Millers claiming promotion to the Championship, scoring in the penalty shootout victory in Sunday's play-off final over Leyton Orient.
Boro triggered a clause in his contract to keep him at the Riverside for another year, though that could have been so they could command a fee for the 23-year-old.
Millers boss Steve Evans is known to be keen on a deal and Smallwood thinks it could happen.
"I'll enjoy my time off for a couple of weeks and then see what happens," he said.
"Of course there is a chance, anything can happen in football. I enjoyed my time here, I would definitely come back if the move was right. We'll see what happens in the summer."
The time that Smallwood spent in South Yorkshire could work in the Millers' favour, with an incredible season ending in Wembley glory.
He played 13 times for Boro before coming to New York in January, making 20 appearances in the middle of midfield.
It was his first loan spell and he got everything out of it that he could have hoped for.
"I have had a great time," he added. "I wanted to get games and get used to winning, I knew that they were pushing up the table and I wanted to be a part of that. Thankfully I have been and it's brilliant.
"I never thought I would play at Wembley, never mind score a penalty. I've had a great time over the last few months."