Paul Warne’s team are bottom of the Sky Bet Championship while the Magpies could end the day at the top despite Brighton’s 2-1 win against Sheffield Wednesday on Friday night.
But Benitez said: "Because of our position and their position, maybe people will think that it’s easy - but I have memories of the last game against them (in October) and it was quite difficult, so you have to respect all the teams.
“After the game, we can talk about whether it was easy or not but before the game, I’m sure it will not be be easy.”
He added: “What they have is good team spirit; they work very hard and I’m sure, especially at the beginning, it will be difficult.
"If you can score and then they are more open, maybe you will see a different game but from the start I’m sure it will be tough.”
Rotherham interim boss Warne has said ahead of the match that his players would become “legends” if they could pull off a shock victory at St. James’ Park.
But Benitez - who confirmed that Aleksandar Mitrovic and Dwight Gayle would miss the game through injury - smiled: “To be fair, it’s something we have seen during the whole season. We play against teams when they give almost everything against us.
“I watch the games before, and even after, and there’s a big difference in terms of the approach.
“But if you are a top side in the division then you know it can be like this. I’m happy because it means they consider us very strong but at the same time, we have to be sure we do also a little bit more, just in case."