Can I contribute to Roth IRA, when all income went into 401k? I only worked part time for 3 months.

  If I only worked for three months and put all income into 401K, minus what was required in taxes, can I still contribute to my Roth?  If so, can I only contribute up to the amount of income that didn't go into the 401K? IE:  Gross earnings = $7000.00 and all but $700.00 went into 401k, as the $700.00 was for all taxes.  Can I still contribute up to $6500.00 (I'm over 50) to my Roth, or can I only contribute $700.00?