Two characters that I will describe the character traits for are:
The Nurse - she is crude with her humor, boisterous in her actions, maternal in her attitude toward Juliet, and fickle in her decisions of who to side with.
Tybalt - he is hot-headed in his reactions to any Montague, vengeful in wanting to kill Romeo for intruding at the Capulet's Feast, instigating any Montague into a fight/duel, and flippant in his remarks to others, especially Lord Capulet at the Feast.
The character traits I would use for Friar Laurence are: he was cowardly when confronted with people coming to the tomb to discover Romeo and Juliet dead, coniving in planning the so-called death of Juliet, knowledgeable about the effects of herbs, and creative in composing the herbs together to make a fake sleeping potion to try to get Romeo and Juliet back together.
Reference: The Language of Literature Book by McDougal Littell
I would describe Romeo as impetuous, passionate, immature, and immoderate.
I would describe Juliet as innocent, a risk-taker, impatient, and determined.
For Friar Lawrence, I would describe him as trustworthy, well-meaning, good-hearted, and kind.
Enotes has a great section analyzing the characters in the play. Go to the sites below to get some more ideas.