Friar Lawrence is a "priest" who dabbles in herbal remedies and alchemy.
Shakespeare is using Friar Lawrence to point out the inconsistencies of the Roman Catholic religious orders since the English are "protestant" ie. Anglican or Church of England.
Friar Lawrence attempts to help the two young lovers out using potion, but all of his efforts are thwarted by "fate". Friar Lawrence is a coward and runs away from the tomb when he sees Romeo and Paris in there dead. He leaves Juliet to awaken to her dead husband and fiance`.
If anybody were full of good intentions in this story, it is indeed the friar. However, he doesn't forsee the eventual consequences of his plans - such as the possiblilty of the timing going awry - which leads to the eventual suicide of Romeo, then Juliet. He is not held to blame for their deaths, though, and the Prince who had warned the feuding families in the first place puts the guilt of their children's deaths upon them instead.
Note that for the "holy man" he is called, Friar Lawrence turns to schemes involving both stealth and deception to help Juliet "escape" a loveless marriage with Paris. He also plays around with strange concotions, much as a witch doctor or medicine man. His compassion supercedes his wisdom, as his scheme to have Juliet feign an untimely death foils up in the end.
See the eNote reference below for a further character study of the friar.