Jerome does not need permission to cast any cleric spell. During this players turn, Jerome may do one of the following: During phase 3, he may retrieve from his discard pile any non-undead/werebeast ally. Or, during phase 5, he may retrieve any one defensive cleric spell from the discard pile.
Copyrights:
TSR
Wizards of the Coast
Jerome is an interesting card with many options available to him. The first line has the feature that he is immune to the power for the Arch-Druid (189/1st), allowing him to cast any spell he may normally do. This immunity also extends to putting the Talisman of the Beast (75/DR) and still be immune to the Lareth, King of Justice (31/DR). This does not protect his wizard spells (if she attaches something like the Viperhand (103/1st)), as it specifies cleric spells.
The second part of his power is a choice between two options each turn. For an ally deck, during phase 3 (including right when he is first played into the pool), he may retrieve an ally without either the undead or werebeast attribute. There are many good allies available for this and makes Jerome a good addition for any ally deck (or deck that uses a few good battle stopping allies).
The other power can be even more useful, in that during phase 5 (after combat), he may retrieve a defensive cleric spell from the discard pile. Good examples spells to get include: Divine Intervention (81/DL) (to get both a champion and any ally), Thrice Hearty Cup of Balder the Red (1/FR-chase), Intercession (48/RR) (bluelined to defensive), Dispel (400/4th), Locate Object (422/4th), or Atonement (69/IQ).
Any deck that uses these often could do well carrying this card (and with Dispel there, many tournament decks should be expected to carry it).