I have put enough bullets down the barrel of my trusty old Marlin 1895 to melt down and make a car. I felt confident when I was able to get ahold of an Italian copy of a Remington Rolling Block rifle that I was "good to go."

The first round I put in the Rolling Block fit snugly but worked. The second one tighter and the third one wouldn't even allow me to close the action to fire a round.

Having no experience with this I went home and took some full sized cases (without any bell) and tried them in the Remington and they fit just fine.

Questions: Should I not crimp my loads for the RB? Can I taper crimp? Do I not need any crimp?

These will be 'normal' pressure 45/70 loads. I intend to harvest a few animals but mostly shoot at paper and steel.

Any insight to crimping and bullet selection will be appreciated. I am a bullet caster and will happily order any mold recommended if it isn't too expensive or a Lee.

rev, in my rollers I tend to use a taper crimp, but I only use heavy loads of black powder,

I also full lenght resize before each reloading, and keep up on the OAL trim lenght

BPCG shooters don't crimp at all ! single shot BLK Powder of any kind don't need crimped , If you set your bullet so it does not stick in rifling , Crimping for the BPCR events will hinder your accuracy with lead bullets , the crimp will alter the O.D. of the bullet causing flyers .

You need to figure out where the interference is coming from. Crimped correctly there should be no interference from the crimp.

You might seat a few dummys without crimping to see if the interference caused by the bullet contacting the rifling. You can do this by seating a bullet in to the case and then drop it into the chamber. Do not try to close the action until you see the rim fall almost to the same depth that it goes with no bullet in the case.
If it sticks a little bump it back out with a cleaning rod. Never force anything though.
What bullet are you using?
Are you using smokeless powder or black?
Are your planning to use the same ammo in both rifles?
If you are planning to use the same ammo in both rifles you need to load all the ammo to the pressure suitable for the rolling block. And the ammo must be a free fit in the RB since it has limited ability to cam a slightly high round home.
Is your rolling block made by Pedersoli?
If you plan to shoot the same ammo in both rifles do not shoot anymore of your existing Marlin loads in the RB unless they were loaded to low enough enough pressure levels for a RB.
I never had any crimping problems with a 45-70. I tend to go light on the crimp since I never had a lever gun. I used the RCBS seater to crimp as a separate operation by backing off the the seater stem. I switched over to a Lee Crimp die because they are less sensitive to case length.

Well let's see...

I don't intend to use any of my heavy loads for the Marlin in the Rolling Block.

I have been using my own cast 405 grain flat nose as well as my 500 grain RCBS bullets.

I hadn't thought about the bullet coming into contact with the rifling. Perhaps a really tight chamber?

My rifle isn't a Pedersoli. If it is I can't find it marked so.

I have heard some folks swear by the Lyman (and probably others) neck sizing dies in these single shot type rifles; any input?

I will probably get to black powder next years. I have played around with a front-stuffer and some with a cap and ball revolver but not in cartridges.

If you don't crimp at all how do you compress black powder loads?

Even if you use appropriate smokeless loads you have to have some way to keep the bullet in place don't you?

Should be an interesting education.

You need to figure out how to keep your Marlin loads separate from the rolling block if they are too hot for the RB. Otherwise you are asking for trouble and it will be trouble right in front of your face.

The friction fit of a sized case without any crimp works ok in my single shot experience.

I have used neck sizers but not with a 45-70.

I do not load BP but it is compressed with a plug similar to the neck expander. Some guys size them some just sit the bullet on top.

I can't say much about you bullets since you did not give the exact design but but they might just need to be seated either deeper or with less crimp. The case should be sized but no crimp is needed. 30 minutes of trying should tell you.

I crimp all my .45-70 loads in a Lee Factory Crimp Die. I shoot a Magnum Research BFR Revolver in .45-70 as well as my Guide Gun. The heavy crimp I can install with the Lee die prevents the big 405 Gr, slugs from pulling out of the case in recoil with the BFR. Bill T.

I load for single shot with RL 7, no crimp needed.