With all due respect to Heidi, you can't print "rgb". A printer or RIP can convert RGB but a printer will not reproduce the RGB color gamut.
RGB is meant for viewing on a monitor red/green/blue pixels that mix to create the projected colors on a monitor. CMYK is Cyan/Magenta/Yellow/Black which is the ink mixture to create a color range based on reflected light (printed pieces).
One question you can ask that may improve some printed results is what type of files your printer prefers? If printing digitally, some printer RIPS are designed to convert RGD to CMYK, others prefer you convert the files on your end.
When you create the artwork yo have to aware of the colors available in CMYK as opposed to RGB.
Good video to watch on this page.