Foreign Earned Income Exclusion and Roth 403(b) contributions

[Francis]

Does anyone know if an employee who is working abroad for a US employer and who qualifies for the foreign earned income exclusion because of income earned abroad can also participate in the employer's ERISA 403(b) plan with her contributions going into the Roth 403(b) option? In this situation my understanding is that she'll just pay FICA on her foreign earned income but I'm not sure if the foreign earned income also ends up on a W2 and if the IRS allows her to contribute some of her excluded income into her employer's Roth 403(b). Thank you.