The original Roman alphabet lacked the following letters EXCEPT:

The original Roman alphabet lacked the following letters: J, U, and W. The letter J did not exist in ancient Rome, and instead, the letter I was used for both the vowel sound and the consonant sound we now associate with J. Similarly, the letter U was not used as a separate letter, but rather as a variation of V. The letter W, which represents the /w/ sound, was also absent from the original Roman alphabet. It was later added to the Latin alphabet during the Middle Ages to accommodate words borrowed from Germanic languages. Therefore, the letter X is not included in the list because it was indeed a part of the original Roman alphabet.