There are quite a few different answers, but the general consensus is that rose ceremonies are not filmed in one long sequence as we see on TV, but they're instead broken up into smaller parts.

According to The Ashley's Reality Roundup , in 2009, Bachelorette host Chris Harrison said: "Everyones nervous at their first rose ceremony, so we make it real easy for them, and we break [shooting] up into three to five people at a time. Then well stop, just to make sure we dont run into any mistakes. We dont want a [microphone] in his/her ear, we dont want cue cards, we want it as natural as possible."

In 2012, Harrison also told People that the leads "do it themselves" when it comes to memorization.

But a year later, in 2013, season six Bachelorette Ali Fedotowsky told E! News that leads have a producer to help them learn names:

"I am asked this question a lot and there are two answers to this question. Throughout the night a producer is never far from your side and constantly reminds you about everyone's name. She (the producer) has flash cards with the pictures and names of every contestant. It is hard to remember everyone, even with the flash cards. It's all so overwhelming.

"How do you remember the names at the rose ceremony? Well, I doubt many people could remember at 25, so the Bachelor/ette goes into the rose ceremony room and says a few names at a time and then leaves to get the next few names."

On season five of The Bachelor, Jesse Palmer accidentally called the wrong name during a rose ceremony. As The Cheat Sheet reports, Palmer wanted to give a rose to "Karen" but instead gave it to "Katie." After consulting with Chris Harrison, Palmer apologized to Katie and told her that she could stay if shed like, which she did, and he gave another rose to Karen.