The R.O.U.S's are KenKen puzzles, with mathematical sign left unindicated. Solutions follow below.

There is exactly one way to fit all six of the R.O.U.S. solutions into the fire swamp grid so that none of the solutions place a digit over either black square, and so that no square contains two different digits.
A few of the outlined areas in each R.O.U.S puzzle do not have a clue. When the R.O.U.S's are placed in the Fire Swamp, each unclued outlined area overlaps another, as seen below.
Note that the outlined areas form one minus sign and seven plus signs. Using subtraction on the numbers in the minus sign (934) and addition on the numbers in the plus signs yields the numbers 2, 21, 26, 26, 11, 9, 12, and 12 in toptobottom and lefttoright order. Using the standard A=1, B=2 decoding, this yields the answer BUZZKILL.