# How to use \mathrm with capital greek letter and newtx package?

I have macros that use \mathrm. However, if the argument is a capital greek letter, newtx package changes the outcome to a math symbol in T1 encoding. I do not expect \mathrm to do anything on capital greeks but only pass through. Is there any way to get this result from newtx package?

\documentclass{report}
\usepackage[T1]{fontenc}
\usepackage{newtxmath}

\begin{document}
I want $\mathrm{\Gamma}$ to be same as $\Gamma$.
\end{document}

You need to make them mathord not mathalpha so they don't follow the current math alphabet:

\documentclass{report}
\usepackage[T1]{fontenc}
\usepackage{newtxmath}

\makeatletter
\re@DeclareMathSymbol{\Gamma}{\mathord}{lettersA}{0}
\re@DeclareMathSymbol{\Delta}{\mathord}{lettersA}{1}
\re@DeclareMathSymbol{\Theta}{\mathord}{lettersA}{2}
\re@DeclareMathSymbol{\Lambda}{\mathord}{lettersA}{3}
\re@DeclareMathSymbol{\Xi}{\mathord}{lettersA}{4}
\re@DeclareMathSymbol{\Pi}{\mathord}{lettersA}{5}
\re@DeclareMathSymbol{\Sigma}{\mathord}{lettersA}{6}
\re@DeclareMathSymbol{\Upsilon}{\mathord}{lettersA}{7}
\re@DeclareMathSymbol{\Phi}{\mathord}{lettersA}{8}
\re@DeclareMathSymbol{\Psi}{\mathord}{lettersA}{9}
\re@DeclareMathSymbol{\Omega}{\mathord}{lettersA}{10}
\makeatother

\begin{document}
I want this $\mathrm{\Gamma}$ to be same as $\Gamma$.
\end{document}