Roman, 12, was Messing's date at the Women's Project Theater's Annual Gala in New York City on March 27.
The 48-year-old actress took to Instagram to share a snap with her son.
She captioned the pic: "Proud mama".
Roman's father is Debra's ex-husband, Daniel Zelman.
The pair ended their 11-year marriage and 20-year relationship in 2011.
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