There are several ways to look at Friar Lawrence, some more fit than others. I found three of these, but first the basic facts about him.
He is Catholic, when Shakespeare wrote Romeo and Juliet, England was a Protestant country. Many writers of the time made fun of Catholics in their plays, but Friar Lawrence is treated respectfully, and has perfection and faults like everyone else. As a member of the Order of St. Francis, a group of wise and generous priests, he means well throughout the play, many people come to him for advice, and he does his best to help them. Romeo and Juliet trusted Friar Laurence completely, turning to him for his advice, and solutions. He often reminds Romeo of the Church's teachings, and he tries to use his position to end the feud. He's an outdoors man, St. Francis loved nature, and so did Friar Lawrence. He gives a significant description of the dawn, and he knows the plants and flowers well enough to make medicines.
One view holds that he is a foolish old man who sends the lovers to their deaths. I feel that he lives shut away in an abbey and doesn't understand other people's passions. Romeo accuses him of this in Act III: "Thou canst not speak of what thou dost not feel!" (III, iii, 64) Since he can't understand their passions, the best he can do is offer shallow words and philosophy instead of wisdom. I feel his words of caution before Romeo and Juliet's wedding are empty, as is his comfort to Romeo after Tybalt's death. He isn't wise, but awkward, and his allowing the marriage, and giving Juliet the risky potion is partly what kills the lovers.
Worse, he's a coward. If he hadn't been afraid to tell someone (like the Prince) about the marriage, the story could have ended differently....