What is the difference?
Examples that may help: Anbraten is when you brown meats before before you put them in crockpot or in a stew. It just browns the meat.
Braten is when you roast something...like Brat kartoffle meaning roast potatoes.
I googled the definition as well but both mean roast...
Not exactly. Please have a look at the translations given in LEO: "anbraten" is short: sauté. "Braten", on the other hand, rather means finishing the process.
Googling by itself is not necessarily helpful. You need to go to reliable sources such as the two given here (linguee has the additional advantage that is offers bilingual material in which the search term is used).
Another source: LEO