Boy, just read thru the replys and ???.
Here is my 2 cents worth. Rimmed Revolver rounds like the .44Mag and .357 Mag should always have a fairly heavy roll crimp. This is to insure the bullet doesn't move forward in the case under recoil and jam the cylinder.(Heavy bullets are most likley to move.) It also allows the slow burning powders normally used in these cartidges to achieve the proper pressure. This seems to be especially true with the lighter bullet weights.
I have tried both crimped and non-crimped .44 and .357 loads in a Contender Single Shot Pistol and with the heavy Silhouette bullets I think the accuracy is a little better without the crimp .
The .38spl should have a light roll crimp.
The .44 semiauto you mentioned I assume is a Ruger rifle, right? It yes, and its the old model with a tubular Magazine then you should DEFINATELY roll crimp. Same reason as in the revolver..bullet movement under recoil. If its a new Ruger with the box mag you might not have to./I have no experience with this .
Generaly, with bottleneck rifle Cal. , it is not necessary to crimp if the case neck gives a good tight fit but you certainly can it you want to. Roll crimp if there is a cannalure in the bullet
Any roll crimped cartridges should be of uniform lenght to insure the same crimp from case to case. The exception to this is when using the Lee Factory Crimp Die. This is an outstanding Crimp die that i would recommend you try for all your roll crimps.
The .45 ACP should be lightly taper crimped ( just enough to lay the case mouth down on the bullet) The case tension is what holds the bullet in the case on semi auto rounds.
By the way, even though the rimless cartidges are theoreticaly supposed to headspace on the case mouth, they almost always headspace on the extractor.