You can go to any search engine and find tons of information about it. I'm not going to say that much because I'm no expert, so I don't want to give you the wrong information. "Rasta" is short for Rastafarian, the religion/lifestyle they practice. True Rasta's have a very healthy diet, they don't eat anything that is processed/fake, and many are vegetarians. The guy you're thinking of is Haile Selassie, he's mentioned in a lot of reggae music. The Rastafarian colors that many are common with (red/gold/green/black) have a lot of meaning behind it. Red is for blood, yellow is for gold, green is the land of Africa, and black is for the people of Africa. There's so much to get into, you should look into it because it's interesting.