I've known darn few spray men who were consistant enough to not need their work backrolled....Conditions, materials, skill with the gun all need to be there in order to get away with it often, though I've met a good number of cocky painters who talked a great talk, but wound up blaming their equipment or cheap materials when they had spraylines, fingering, puddling and holidays....The wall will have a bit to say about it as well, the more textured, the more forgiving...
A certain mindset is required to spray "perfectly". You need to pay intense attention to your work (good luck with all that, especially on a construction site). HVLP is designed to NOT be backrolled, but go ahead and try to spray out an interior with a cup gun!! You'll definitely wind up with "Popeye" forearms!!
The best advice I can give you if you have no choice but to spray sans backroll is to thin your material a little, use a smaller spraytip (like a Graco 413), and use a vey fast arm motion with your gun ALWAYS in the same direction (no arcing, use your wrist to keep the gun perpendicular to your work at all times) and at the same distance from the wall with a very consistant speed....And you'll need to experiment with rig pressure to find the "sweet spot"...New tips often "finger", leaving a trail outside the spray pattern that WILL show if not backrolled. Sometimes a little more pressure will help to minimize this effect, but your best bet is to adjust your distance from your work--the closer you are, the more prominent those fingers will be...
Good luck