Took a look at some numbers.
GF under Lindy 46 or 2.71 per game
GA under Lindy 56 or 3.29 per game
GF with Rolston 14 or 2 per game
GA with Rolston 20 or 2.86 per game
So both GF and GA go down with Rolston but goal differential goes up from -0.59 to -0.86