Painting - Smooth Finish?

Have a beautiful custom made desk made from Birch plywood. Started with a coat of primer, then sanded. next I used a 3/16" roller to apply the first coat of semi-gloss. Upon drying realized it is not as smooth as I had hoped for.

Should I have used a brush to apply paint? If so, what is the needed coarse of action to take? Or am I just plain out of luck?

Thanks for any help.

A roller will leave a orange peel type texture if not brushed out, roll a section, pick up the brush and lay down the texture, you have to do it quikly or it will look worse than just leaving it rolled. To remedy the existing texture, I will suggest sanding the texture (not nesasarily sanding the paint off) with a 180 grit, followed with a 220 grit and re-paint, if you use the roller don't get ahead of yourself before brushing out the roller texture, one section at a time, some parts are better just to brush. The roller can leave little fibers also, so you may want to consider brushing all of it. Thinning the paint will help reduce brush marks, just watch carefully for runs and sags.