Frier lawrence is the priest who Romeo wants to marry him and Juliet.
I think that Frier's role is to marry them, but also be there for both Romeo and Juliet.
"Wisely and slow... They stumble that run fast" could be a warning to Romeo that is he rushes things too fast, bad things might happen.
It would be wise of him to take things slow.
yes...but will he? He's impulsive!