Cait Sith isn't the easiest character to play in Final Fantasy 7 Rebirth, especially when you first get him, but he is certainly the most fun. One reason for this is the unpredictability of his attacks, much like Roll o' the Dice. Here's a list of his effects.
Final Fantasy 7 Rebirth – How to play CAIT SITH! Combat Tips & Tricks Guide (FF7 Rebirth)
Roll o' the Dice can roll a number between 1 and 6. They all have pretty good effects, except 2, which is just useless, not bad. Here is a list of the effects.
Related: Best Synergy Skills and Abilities in Final Fantasy 7 Rebirth
The great thing about Roll o' the Dice is how you can manipulate the number that appears by throwing it around before it comes to rest. This allows you to take advantage of some truly amazing moves for only 1 ATB meter, depending on the situation.