[quote=@Sho Minazuki]
Roll a dice and assign rarities to the results? Like if you get from this number to this number it's a <rarity status here>, and once rarity is decided, roll again for what Pokemon in that rarity range will appear.
[/quote]

yea its easy to roll for a rarity range

its just rolling for the pokemon q.q honestly have no clue how to do it,