Translation:He has been drinking beer since he was nine.
Yes. This is the firt place this word is taught. There are two expressions for 'years' in czech. ROK and it has plural ROKY and a word that is never really used in singular and plural is LÉTA. It does come from the word léto but I do not think that native speakers really realize it till a foreginer points it out. It cannot be used in singular as it would mean just a summer. I believe that you can come across this in some archaic English as well. In archaic Czech you can sometimes also come across the word ZIMA (winter) being used as an expression of a year. Dožil se ještě mnoha zim. = He lived to see many more winters. But you would not hear that in spoken language.
You can use (in plural) both words = roky and léta as you wish. They are equal. I personally would probably use LET in majority here, it just is easier to pronounce. Flows better. But it might be personnal preference.