How to pronounce "potassium manganate(VII)"? The formal names for such inorganic compounds having metals showing of variable oxidation states involve use of Roman numerals, for example "copper(II) sulphate" or "potassium manganate(VII)" or "hexaaquacopper(II)". Of course, common names like "copper sulphate" or "potassium permanganate" do exist, but if I wanted to use the formal ones, how do I correctly pronounce them?
Simple: Just read the roman numerals as a number.

Copper-two sulphate
Potassium manganate-seven
Hexaaquacopper-two.

For negative oxidation numbers use a minus:

Tetracarbonylferrate-minus-two ($\ce{[Fe(CO)4]^2-}$)