Short for "I would roger that" or "Would you roger that?" (If a question)
Military (Marine Corps) slang combined with the British slang roger
. Most commonly used by Unites States Marines to establish that they have seen a woman they think is worth having sex with. It is a much more crude way of establishing a woman is attractive.
Normally one Marine will notice a woman, and as she is walking away he will say to his comrades, "Roger That." to which they will reply, "Roger that." (Or they will hit him and demean him if she is a butter face
or just plain ugly)