Chromium(II) ion

or

Chromous ion

Chromium(III)

or Chromic ion

cobalt(II) ion

or 

cobaltous ion

Cobalt(III)

or

Cobaltic ion

copper(I)

or

Cuprous ion

copper(II)

or

cupric ion

iron(II) ion

or 

ferrous ion

iron(III)

or 

ferric ion

lead(II)

or

Plumbous ion

lead(IV) ion

or

plumbic ion

nickel(II) ion

or

nickelous ion

nickel(III)

or

nickelic ion

silver ion

note: silver has only one oxidation state

no roman numeral required

tin(II) ion

or 

stannous ion

tin(IV) ion

or

stannic ion

zinc ion

note: zinc has only one oxidation state

no roman numeral required

Gold(I) ion

or

aurous ion

gold(III) ion

or

auric ion

mercury(I) ion

or

mercurous ion

this ion contains two(2) Hg atom, when the separate ion is written it requires []

mercury(II) ion

or

mercuric ion

this ion contains one(1) Hg atom, when the separate ion is written it requires []

bismuth(III) ion

or 

bismuthous ion

bismuth(V) ion

or 

bismuthic ion

antimony(III) ion

or 

antimonous ion

antimony(V) ion

or 

antimonic ion

cadmium ion

this atom has only one(1) oxidation state

no roman numeral is required.