How works re roll skins? i have skin 1829 + legacy + new twitch, give me great skin or nah?


It is completely random. You have the same chance of getting a good skin if you reroll three 520 rp skins as if you reroll three legendary skins. So don't reroll expensive skins
I wouldn't risk a 1820 skin on a reroll. I have about 20 or so skin shards of varying values of champs I don't (really) play just waiting for when I get a decent skin in a chest, to then disenchant so I can buy it. My last reroll was 3 520 skins and I got Star Guardian Soraka.
only advantage to rerolls is the new skin is a full skin and not a shard so if you are lucky and get a skin for a champ you own you get the skin absolutely free. but if you do not own the champ then the skin sits in your loot and can be disenchanted.