References to the phrase "rough, tough, and hard to bluff" are surprisingly rare, and mostly recent. These are the oldest I could find:

"Then there were some from Waukegan, who were 'rough, and tough, and hard to bluff' who expected to win six or seven championships for Hillsdale...."
--from The Winona (Hillsdale, Mich.: Hillsdale College, 1925).

"Bogie (that's what everyone calls him) may be rough, tough, and hard to bluff before a camera, but, face to face, he's pleasant and friendly...."
--from The American Magazine, 1943.

"They are the prisoners who must prove 'rough and tough and hard to bluff.'"
--from The Journal of Criminal Law, Criminology and Police Science, 1954.

"...Read all about it/We've got a team/And we're proud to shout it/We're rough, we're tough/We're hard to bluff/Conesville Vikings/Strut your stuff..."
--from Cheerleader Handbook by Carolyn Frances Bruce (Fond du Lac, Wis.: National Sports Co., 1960).