Can I still contribute to Roth IRA at $6500 even after maxing out on the company's 401K at $24500 for 50+ year of age?

I've maxed out on my company's 401K at $24500 (50+ years of age) for year 2018.  Can I still contribute to Roth IRA on my own for maximum $6500?  And since the Roth IRA Is an after tax account, there's no tax credit on the annual tax return, correct?