Hahahahaha unfortunately they don't go to the beach ^^" (but I do have a doujinshi that they all go to the beach

)
Hm, I can't remember exactly what happened in the novel, but I'll try to do a summary ^^"
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I think, in this "holiday", Roy was sent to supervise the training of the army in another city. But those soldiers didn't even know how to hold a gun, so you can imagine the headache Roy would have in there u.u"
Later Hughes and Armstrong met with Roy, because they were investigating something (which I can't remember @_@") around there and ended up in the city's headquarters. By that time, Roy was already all stressed so Hughes suggested that they should do a hiking (haikingu? XD), instead of drinking, like Roy suggested XD.
During this hiking, they crossed a bridge that broke, leaving them on the other side and it was impossible to return from that way. While they were looking for another way, they found a small village, where mysteriously only children lived in O_o. Since it was already night they decided to spend the night there. Of course they would pay the children for renting a room, but they lost their wallets when the brigde had fallen XD. So Mustang-tachi and the children made a deal: the colonel and the others must work during one day in
exchange for food and a place to rest. Armstrong helped the kids to fix some roofs and others things in their houses, Hughes helped them with something dealing with paper (I couldn't understand this one @_@"), and Roy... well, there wasn't anything he could help with his speciality XD (and a boy began to tease him about his uselessness XD). So Roy ended helping a girl with the chores at her house, like cleaning, washing the dishes and peeling vegetables XD. But as he didn't know how to do these things, the girl (I guess Rose was her name) constantly teached him how to do each chore. Seeing the patience and kindness that she teached him, he learned that he should be more patient and kind with his subordinates too ^^.
Of course, there was much more in the novel, but I don't feel like writing all about it because I'm not entirely sure of what happened (my japanese is pretty poor) and I don't want to spoiler it if you're going to read it in the future ^^
But I can tell that in the end Roy was back at Eastern Headquarters, trying to be kind with his subordinates, but everyone treated him back like usual (and they weren't very nice XD), giving him tons of paperwork. Later Hawkeye arrived at his office, bringing a picture Hughes sent her. The picture was Roy using an apron, peeling vegetables and with a lot of bandages on his fingers XD. After a while, the entire headquarters knew about the picture, entitled now with "Roy's apron", leaving Roy all like "...no one is nice to me... T_T"
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Note: I'm sorry if it was confusing, it's because neither english nor japanese are my languages @_@"
I scanned some illustrations (I scanned only the ones concerning Roy-tachi, if anyone wants the others, ask me ^^):
http://img.photobucket.com/albums/v303/ghi/novel4scan.jpghttp://img.photobucket.com/albums/v303/ghi/roysholiday.jpg <== I guess this one is from Hughes' picture