Remember that there are different versions of Shakespeare's plays around, but that said, in my version, line 24 of that scene reads as follows:
"O that I were a glove upon that hand,"It fits with line 25:
"That I might touch that cheek!"
In these lines, Romeo is wishing that he could touch Juliet, and expressing it poetically. If he were a glove, her fingers would be touching him—she'd be inside him, so that even though this says nothing literal about sex, this is quite a sexual image. It is also very gentle, though.
ROMEO: "See how she leans her cheek upon her hand!
O that I were a glove upon that hand,
That I might touch that cheek!"
In Act II Scene II, Romeo is spying on Juliet. Line 24 is near the end of his romantic spying monologue. She is above, in the balcony of her room, and he is below, completely entranced with her beauty and innocence.
"Oh that I were a glove upon that hand, that I might touch that cheek," is pretty self-explanatory when you break it down. Romeo is so entranced with Juliet that he would be happy to simply touch her cheek--to be near her in any way--even if it means being an inanimate object--a glove on her hand!
Remember--Romeo and Juliet are teenagers, and they have just met at a costume ball. Both fell for each other hard--so hard that Romeo completely forgot about his girlfriend Rosaline, who he lovingly discussed earlier in the play with his cousin Benvolio.
Juliet has so captured Romeo--his heart, his head, his body, his lust, his affection, that it is as though he sees only her. His life, in these few moments, has changed focus to Juliet and Juliet only, regardless of the danger (perhaps even a little because of the danger), regardless of the consequences, regardless of what this could do to their families, to Rosaline, and, as we find later in the play, to Juliet and Romeo themselves.
Lines 24-26 of Act II Scene II are simple and romantic--the longing of one to be with his lover, in any way possible.
ActII sc.2: "See how she leans her cheek upon her hand/O that I were a glove upon that hand/That I might touch that cheek!"
Romeo is now infatuated with Juliet. She appears above him by leaning out of the open window and resting her cheek on her open palm. Right now she is literally out of his reach and he expresses his longing for her by saying that he wishes he were the glove that Juliet is wearing on the hand that her cheek is resting on so that then he will be able to cup her cheek in his hand.