how to go about doing this?

I made a drop system recently and now i need to combine it with my party system.
problem is when uncommon or higher class items drop how can i make it so all players in the party who killed that mob must roll, and highes roll gets that item, plus more than one could drop, like 3 uncommons or uncommon, epic
it uses a corpse like system. when a mob dies, ir spawns a bag containing items it drops.

i would like it so players click like a button to roll for item.

you could have maybe like a system, when a unit dies, create a few items or whatever and set them in an array, set unit group to allies, pick random unit, give first item to him, set integer = integer + 1(for your item array so you use em all), remove unit from group, rinse and repeat

is that something like what you want?

no, i want each player to do a roll on each item, a roll will randomly pick a number from 1-100, player with the highest roll for that item gets it.

Take a look at how WoW handles uncommons, rares, and epics in groups.
that will show exactly what i want to do.