Speaking after his side's 2-1 friendly win at Saltash United, Boro chief Neil Warnock - when asked about incoming transfers and a move for Crooks - said: “We’re quite close at the minute to getting a couple over the line this week.
“Crooks is one we’ve been talking about, but there’s a couple more we’ve been talking about too.
“If we can get a couple over the line, we’ll be delighted."
Ex-Huddersfield Town and Northampton player Crooks has the subject of intense speculation so far this summer.
Ipswich had seen several bids rebuffed by the Millers for the 27-year-old, who has a year left on his contract and an unnamed second-tier club made a bid last week.
Crooks - who enjoyed a strong 2020-21 campaign and was named as the Championship's player of the month for January - is reportedly set to undergo a medical at the Teesside club later this week after a fee was agreed with the Millers.
Boro are also hopeful in their quest to get a deal over the line to sign Argentine midfielder Martin Payero.
“You always want to get players in as soon as possible, but sometimes you have to wait for the right ones," Warnock said.
“We’ve got four in and if we can another couple in the next ten days and hopefully Payero after the Olympics we won’t need much more."