Can I contribute to a traditional or Roth IRA if I’m covered by a retirement plan at work?

Yes, you can contribute to a traditional and/or Roth IRA even if you participate in an employer-sponsored retirement plan. However there are some contribution limits, here is an article from the IRS website that discusses IRA Contribution Limits.

Also note that if you or your spouse is covered by an employer-sponsored retirement plan and your income exceeds certain levels, you may not be able to deduct your entire contribution. Here is another link to the IRS page that covers IRA deduction limits.