So, just using a spreadsheet as I don't know how to do an equation for it, for a single die roll, I got to 66.2% win rate and 9.7% tie rate(up from a 41.7% win and 16.7% tie with no rerolls) rerolling a single die (assuming that on losses where your own die is 3 or less, you reroll your die, and on losses where your own die is 4 or higher you reroll their die). I believe my math is correct... and I think if I had hours and hours I could possibly figure it out for 2 die rolls, but I'm hoping either someone has done this, or someone can actually create an equation.
Edit: Ugh, I realize that in situations such as me rolling a 3 and them rolling a 6, it's for sure better for me to reroll their die rather than mine with only a single reroll. So my premise above is wrong for sure, the number should be higher.