They're not exactly the same. RZR wheels are 1/2" wider than ATV rims but the offset is close according to the RZR model. Many of the RZR's use 12" wheels that won't work on your machine.
I all depends on which RZR model you're talking about.
The Polaris catalog gives the offset in mm for the cast rims right in the description.
Looks like the 2019 RZR 1000 XP wheels should work on your 850sp. Given the 1/2" greater rim width along with a little more offset, they are within about 1/4" of being the same.
The RZR wheel studs are bigger: 850sp are m10-1.25
RZR 1000 are m12-1.5
Not sure if that would be a problem or not? I suspect they'd bolt up just fine but...
Your fronts are 5.5" wide with a 46.7mm offset (1 27/32"): RIM-FR,CST,NO MACH,14X5.5-46.7
Your rears are 7.5" wide with a 57.4mm offset (2 17/64") : RIM-RR,CST,NO MACH,14X7.5-57.4
The 1000 xp RZR front 6" wide with 53mm offset (2 3/32") RIM-FRT,14X6,CAST,53,FLASH BLK
Rears 8" wide with 63.5mm offset (2 1/2") RIM-RR,14X8,CAST,63.5,FLSH BLK