Translation:In my room, there is a big round table.
According to what I have learnt and to the Wiktionary, it should be noted that 丸い can be replaced with 円い as a graphical variant.
Nevertheless, I don’t know if there are any semantic nuances between the two.
PS: well, I have my answer thanks to IsolaCiao in this thread! It turns out that there is a difference is usage; see his hyperlinks.
大きい and 小さい are い形容詞 in terminal form but な形容詞 in attributive and continuative forms.
It did not accept "in my room is a big round table." Is there something inherently wrong with this translation?
Nothing wrong with it. What's you've put is a grammatical English sentence with an almost identical meaning.
Its meaning is completely identical, not just almost. It should accept both ideally, though it's understandable that it wouldn't get this right at first, instead opting for only the most word-for-word translation.
I had the same thought. The best guess i can come up with is that it's similar to how we list attributes in English: "I have a big, yellow, spacious, submarine."