How can I display equations with long spaces between them?

I have used enumitem with the option roman to have (i), (ii), etc. labels and I have given a space of 18pt between the formulas, but you can choose differently.

documentclass[a4paper,12pt]{article}
usepackage{amsmath,amssymb}
usepackage{enumitem}


begin{document}
setlengtharraycolsep{18pt}
begin{enumerate}[label=(roman*)]
item First roman enumerate
item If $theta$ and $psi$ are formulas, then so are [begin{array}{*{5}{l}}
negtheta & (thetawedge psi) & (thetaveepsi) & (thetatopsi) & (thetaleftrightarrowpsi) 
end{array}]
item Third roman enumerate
end{enumerate}


end{document}

Peraphs with other math fonts like MnSymbol you can obtain the similar symbols.