I am a hand quilter, but I have two large quilt tops I want to have custom machine quilted. I have the batting and the backing. How do long arm quilters like to receive the tops for quilting? When I find someone to do the quilting for me, I will ask them their preferences, but now while I am preparing them, I would like some general guidelines.

Google "Preparing a quilt for longarm quilting". There's a ton of information on it You'll see what's the same for most of them.

I like the top, the backing fabric and the batting not put together. I have to put them on rollers on the long arm.

Your top should be pressed, loose threads clipped/removed, if there are a lot of seams along the outer edges it is a good idea to stitch a running stitch all the way around the outer edge of the quilt, about 1/8" in- this keeps those seams from pulling apart as the quilt is advanced on the rollers. If the quilt is directional it is good to mark the top, indicating the top (backing too) each piece, top, batting, backing is loaded individually so they need to be separate pieces, neatly folded. The backing and batting needs to be larger than the top to accommodate being loaded and clamped ( each quilter has their own preference on how much bigger- I usually ask for an extra 4"-5" all the way around, so if the top is 70" X 80" the batting, backing should be about 80" X 90")