I Ain't Mad at Cha

All Eyez on Me 2Pac
Rolling is used here like "riding", which is going out looking to get revenge on somebody. Having 'Pac's back means being with him to help him.
when its time to fight(roll) you will fight with the friend you are hanging with.
smoking weed that is particularly good until you reach a wonderful high or stoned state
Was sent to the Youth Authority and came back with large (swollen) muscles from lifting weights during the sentence.
Spent time at the Youth Authority (Minor version of Jail) and after released, went back to the old neighborhood with a large ego
A buster is a derogatory term for someone who represents the color red in a Blood or Norteno gang, and he is implying that he will take them out or beat them up.
He has a great idea to make money and someone doesnt agree with him about it, if it would work, and/or its premise
Out on the street carrying a Glock pistol intoxicated from smoking cigarettes dipped in embalming fluid, known as sherm.