"Is that a real rose?"
Translation:Ĉu tio estas vera rozo?
Because the point is not whether "that" semantically (by meaning) refers to a rose, but whether it grammatically (by position etc.) modifies the word "rozo" in that sentence.
In this case, it stands by itself grammatically; it's a pronoun. It is not "that rose" but simply "that", by itself.
And the demonstrative pronoun for objects is "tio".