two words from a dialogue
The following dialogue is from the TV - Gray's Anatomy.

Meredith: We're having sex every night. I think I deserve details.
Derek: You have more details than most.
Meredith: I want facts, and until I get them, my pants are staying on.
Derek: Or you could just roll with it. Be flexible. See what happens.
Meredith: I'm not flexible.
Derek: There I disagree. Hmm. I've got to go. We'll find these things out. That's the fun part. You know? That's the gravy.
Meredith: I don't want to be your gravy.

1. I know the meaning of "roll", but I can't imagine what "roll with it" looks like? with the pants on but roll the pants leg up and expose part of your leg?
2. What does "gravy" refer to in this context?

Thank you.

Question

two words from a dialogue
The following dialogue is from the TV - Gray's Anatomy.

Meredith: We're having sex every night. I think I deserve details.
Derek: You have more details than most. 
Meredith: I want facts, and until I get them, my pants are staying on. 
Derek: Or you could just roll with it. Be flexible. See what happens. 
Meredith: I'm not flexible. 
Derek: There I disagree. Hmm. I've got to go. We'll find these things out. That's the fun part. You know? That's the gravy. 
Meredith: I don't want to be your gravy.

1. I know the meaning of "roll", but I can't imagine what "roll with it" looks like? with the pants on but roll the pants leg up and expose part of your leg?
2. What does "gravy" refer to in this context?

Thank you.

Answer

Quynh is right about the first question.   As to “gravy,” “gravy” means an additional benefit that makes a good situation even better.  The idea is like: Meat is good, but it’s even better when there is gravy on top.  The expression is usually used to mean that you would be happy with and agree to a situation or agreement that had benefits A, B,  and C, but there’s a chance that you will also get benefit D which would make the situation/agreement even better.  Benefit “D” is “the gravy.   Here, Derek appears to be saying:  Having sex with Meredith every night is great.  But keeping Meredith in the dark about whatever details she is asking for makes the situation even more fun for him.

Answer

Interesting question:) I'm not a native so i can only answer the first one.
The meaning of ''roll'' here isn't like you literally roll something, like rolling your sleeves or your pants up or like springrolls. ''roll with it'' means going along with things, without high expectations; adapting to a situation despite unexpected circumstances or challenges.