How do I get a bright colours?

Trying opening your file in rgb mode and printing direct to your Roland. It's still going to get "converted" to cmyk but your printer RIP may have a different algorithm then Illy. Probably not, but worth a test print.

Will the Roland be the printer that also runs the final print run? Or do you just use it for layout purposes?

Inkjet printers can sometimes be able to produce much brighter colors than are possible in offset printing. So first of all it would be necessary to find out what can be produced on the final run.

If you want to print a color it is always a good idea to see how the color looks on paper. Print colors can not be selected on a screen in a reliable way (Not even with the best calibrated screens). A screen emits light as opposed to paper that reflects light. There are printed color book for CMYK colors and different companies that offer spot colors have also similar samples (like Pantone or HKS).

Your color is unprintable unless you use a dedicated spot color. Yes, it's CMYK having a limited gamut plus of course in order for this to have any meaning you would need to use color management. Start here:

https://helpx.adobe.com/photoshop/using/understanding-color-management.html

If you really want "neon" colors things get even more complicated, since the whiteness and reflectivity of the print medium matters just as well. Some of this stuff can be faked to some degree by reducing the density of the print color so more reflected light comes through, but there are of course limitations. Anyway, it's complicated...

Mylenium