Boro suffered their first defeat of the summer when they were beaten 2-1 at York earlier this week, and Warnock will be hoping to regain some momentum ahead of next weekend’s season opener at Fulham.
Here are a few things to keep an eye on.
Can Boro find the right attacking combination?
Following his arrival from Wycombe this summer, new Boro striker Uche Ikpeazu has impressed during pre-season.
The 26-year-old made an excellent first impression when he scored a stunning opener at Bishop Auckland and has held the ball up effectively when it has arrived at his feet.
Against York, though, Ikpeazu lacked support when he tried to press opposition defenders, and was forced to make runs into the channels to stretch the hosts’ backline.
Jamie Paterson and Matt Crooks were deployed as attacking midfielders in a 3-4-2-1 system but struggled to link up with the side’s striker.
Paterson, who is on trial at Boro after being released by Bristol City, is likely to get another run out against Rotherham but will need to make more of an impact.
Marcus Tavernier and Duncan Watmore could also return, which should help provide more support for Ikpeazu as Warnock searches for the right attacking combination.
What about Boro’s left side?
Warnock was quick to point out his side’s lack of left-footed defenders following the York game.
Regular left-back Marc Bola is likely to remain sidelined for the Rotherham fixture, while Hayden Coulson, who has been heavily linked with a move to Ipswich, has also picked up a knock.
With the pair absent, Djed Spence played the first half as the side’s left wing-back at York, when Boro struggled to create chances on the flanks.
WIth just over a week to go until their season opener against Fulham, Warnock may have to find a short-term solution to the problem.
Boro have been trying to strengthen at the back, with Cardiff’s Ciaron Brown and former Sheffield United defender Kean Bryan on their radar, though both have predominantly played at centre-back.
Whether Warnock is forced to change his system or find a temporary solution, it’s an issue which needs addressing.
Will Sam Morsy and Jonny Howson play together?
While both players clearly have a lot to offer, some will ask if Boro need to start games with two holding midfielders.
The pair did play together regularly last season, though Morsy was often pushed further forward into a less natural box-to-box role.
Howson, who was making his first appearance of pre-season, played alongside Morsy at York, and it seems likely they could both start for the tricky away game at Fulham.
It’s a combination which would give the side a solid base in the engine room, but Boro would also need the players in front of them to pose enough of an attacking threat.
That will be more challenging if Warnock sticks with a back three, as the side’s wing-backs are often players known as full-backs rather than more offensive wingers.