In a way, yes.
For the sake of avoiding confusion, I'm using the terminology:
Dungeon - the painting you choose
Stage - sections within the dungeon that individually cost an amount of stamina
Rounds - waves of enemies within a particular stage.
In normal use, you'd do an entire dungeon, get loot from the boss, then be kicked back out. If you want another shot at the boss' loot table you need to redo the entire dungeon.
With the caveats that:
- It appears loot is determined when you start a round or stage (irrelevant as per later point)
- You can disconnect from the internet (i.e. airplane mode) on the last round of a stage and the game won't throw a fit, and yet still see what the boss drops
You do exactly that (airplane mode on the last round) and see if
a) the boss drops what you want. If it is, (Black Cowl, etc) you reconnect by disabling airplane mode and let the server process the fact that you did defeat the boss.
OR
b) the boss does NOT drop the loot you want. Close the app before disabling airplane mode, restart, do NOT select continue (since the loot is the same) and just redo the entire stage for its stamina cost to reroll loot.
Repeat b) till you get the drop you want.
Essentially it cuts rolling the boss' loot table from a dungeon's entire stamina cost to the cost of that single stage.