I could not find any quotes on dress robes used by the twins. But based on Mrs. Weasley's statement, all of her kids got secondhand clothes. It could be Ron's bad luck that there weren't any good robes of his size.
“Don’t be so silly,” said Mrs. Weasley. “You’ve got to have dress robes, they’re on your list! I got some for Harry too... show him, Harry...”
In some trepidation, Harry opened the last parcel on his camp bed. It wasn’t as bad as he had expected, however; his dress robes didn’t have any lace on them at all - in fact, they were more or less the same as his school ones, except that they were bottle green instead of black.
“I thought they’d bring out the color of your eyes, dear,” said Mrs. Weasley fondly.
“Well, they’re okay!” said Ron angrily, looking at Harry’s robes. “Why couldn’t I have some like that?”
“Because... well, I had to get yours secondhand, and there wasn’t a lot of choice!” said Mrs. Weasley, flushing.
Harry Potter and the Goblet of Fire, Chapter 10, Mayhem at the Ministry
Digging up bit of history to substantiate my points:
“That lot won’t come cheap,” said George, with a quick look at his parents. “Lockhart’s books are really expensive...”
“Well, we’ll manage,” said Mrs. Weasley, but she looked worried. “I expect we’ll be able to pick up a lot of Ginny’s things secondhand.”
Harry Potter and the Chamber of Secrets, Chapter 4, At Flourish and Blotts
The Weasley kids normally got secondhand stuff.
“The diary,” said Riddle. “My diary. Little Ginny’s been writing in it for months and months, telling me all her pitiful worries and woes — how her brothers tease her, how she had to come to school with secondhand robes and books, how —” Riddle’s eyes glinted “— how she didn’t think famous, good, great Harry Potter would ever like her...”
Harry Potter and the Chamber of Secrets, Chapter 17, The Heir of Slytherin