"Physically, the Boks are on a different planet to a lot of other nations," said Rowntree, a member of the England coaching staff when South Africa won 42-6 in London last November.
"They've got some really big men and they've got some incredible athletes too. They're big, fit men.
"You think of their pack that toured here in the autumn; it contained the likes of Bakkies Botha, Victot Matfield, Danie Rossouw, Pierre Spies, Schalk Burger, Juan Smith, John Smit, the list goes on.
"I remember when England played them at Twickenham, you had Botha and Matfield making try-saving tackles and covering ground as well as dominating collisions and dominating the lineout.
"But we have to make sure we're not daunted by that."
Having toured the Republic with the Lions in 1997, Rowntree knows what it takes to win on South African soil. The former Leicester and England prop understands that talent alone will not secure a place in the history books.
Only hard graft, team spirit, strength of character and a willingness to put bodies on the line will provide the Lions with the necessary platform to match the achievements of 12 years ago but Rowntree believes the class of 2009 have just what it takes.
"We have to match the intensity that they will bring to the game. You have to bring an element of physicality as it will be a war of attrition.
"The Springboks at home against the Lions is just special. It's a special atmosphere and we have to match that intensity, physicality and desire, which I'm sure we will do.
"Our guys have been playing a high level of rugby week-in-week-out but we had to take the right animal on this tour.
"It's a special challenge. On international tours nowadays you only normally play a couple of Tests and then come home. We're going there for more than six weeks. You need some special characters. There will be low times and you need big characters to lift the team.
"If you take guys away from their friends and families for seven weeks, that's a big ask. You take them away and ask that they play hard games week in, week out and travel twice a week, that's an even bigger ask. You need a certain type of player to be able to do that.
"I'm always confident, though. We go in as the underdog and I like that tag, but the players we've put together as a squad are a special group."