In LOR, the main way outcomes are resolved is through rolling dice and adding your modifier. For almost every type of roll, your character often will have a modifier stated in your character sheet that will be added, or some instances subtracted from your roll.
There are two types of dice, normal and split dice.
Normal dice refers to these dice:
D4
D6
D8
D10
D12
Split dice refers to dice, that you take a normal dice and take half the value.
D3(Take the value of a D6 and half it, rounding up)
D5(Take the value of a D10 and half it, rounding up)
When you apply modifiers or are doing any form of calculations you apply it in the following manner
1. Positive modifier
2. Negative modifiers
3. Multiplication
4. Division
Advantage refers to rolling two dice and taking the highest. Disadvantage refers to rolling two dice and taking the lowest role.
Everytime you end up with a non integer after calculations, you always round down unless stated otherwise.