The Whiskey Rose perk allows the player to consume alcoholic beverages without suffering any negative effects, including negative effects due to addiction. Additionally, consuming whiskey will raise the player's DT by 2 to 6 points and consuming wasteland tequila will raise the player's DT by 3 to 9 points, all based on the player's Survival skill.
This perk does not remove the possibility of becoming addicted to alcohol, but merely eliminates the negative effects from alcohol addiction. The duration of the addiction remains unchanged. Losing Cass as a companion will cause negative effects to be applied if the player is currently suffering from alcohol addiction.
The original idea for this perk was that you could carry more water items, along with receiving a healing bonus from its consumption. This was then changed to become more valuable as a companion game mechanic, and to also reinforce Cass's hard-drinking personality.