Avoiding Satin Paint Streaks with Roller
By streaking in satin paint I assume you mean flashing. Flashing is when you can see differences in sheen at certain light angles that looks like you just went over some areas with wet paint and other parts look dryer.  It's more noticeable with higher sheen paints and oblique lighting like you might find from a nearby window on an adjacent wall. Does that sound like what you mean by streaks?

Flashing was something I always had a problem with. One of the things that leads to flashing is I believe an uneven coat. When I keep the roller consistently loaded I don't get flashing.

The W technique never worked for me and I don't think I've seen a professional painter roll on paint that way. What I've always seen them do is roll up and down the wall just the width of the roller. Then reloading and doing the next strip.

What I do is load the roller, roll off the excess in the pan, start in the middle of the wall, roll up, then down only 3 or 4 times. Reload, roll of excess, overlap the next section a bit. When I'm done rolling the next stripe I will roll back over the previous area slightly to even out any roller marks. Also I stopped trying to squeeze the most I can out of the roller when I'm almost done painting and I'm almost out of paint and too lazy to deal with opening another can. Keeping a consistent level of paint on the roller, not pressing it too hard and just letting the paint do the work has helped a lot. 

If you move down the wall and notice you may have missed a spot on an earlier stripe, just leave it. Touch it up after it has dried enough for the next coat.  

I also have one of those Wagner power rollers that pumps paint into the roller which makes it easy to keep the roller consistently full of paint. When I use that I've never had flashing issues.

Lately I've started using Benjamin Moore Aura which is really good when it comes to flashing. I wasn't sure if it was just the paint or my technique until a few months ago when I had to do some painting with a non Aura eggshell finish paint and I didn't get any flashing even though I did it fairly rushed using a roller and tray. The other paint is a good paint but I've had trouble with flashing in the past. Especially on ceilings.