Using Roman Numerals to indicate a compound
No, those are two distinctive species with different names:


$\ce{CuCl2}$: copper(II) chloride;
$\ce{[CuCl4]^2−}$: tetrachloridocuprate(II).


Oxidation number denoted with the Roman numerals in parentheses refers to the element it's placed after and doesn't carry any additional information besides the fact that copper exists as $\ce{Cu^2+}$ in both compounds.

Nomenclature rules were designed that way so that a name would unambiguously define a single compound only (I'd suggest the Red Book's Nomenclature by IUPAC [1] as a reference).

References


IUPAC “Red Book” Nomenclature of Inorganic Chemistry, 1st ed.; Connelly, N. G., Damhus, T., Hartshorn, R. M., Hutton, A. T., Eds.; IUPAC Recommendations; Royal Society of Chemistry: Cambridge, UK, 2005. ISBN 978-0-85404-438-2. (PDF)