You need to add where the Rostam is stored (example bag="Wardrobe 3) and make sure to keep them in separate bags, and not move them.
Also, you wont be able to swap between the two examples you have since both have both Rostams in use (Can't swap and equipped weapon from main to sub or vice versa). To do this efficiently you will need to use modes and not have your weapons listed directly in your sets.
https://github.com/Selindrile/GearSwap handles this well and has a discord devoted to supporting his work.
Then you would use something like this:
sets.weapons.Savage = {main="Naegling",sub={name="Rostam", bag="Wardrobe 4"}, range="Anarchy +2"}
sets.weapons.Aeolian = {main={name="Rostam", bag="Wardrobe 4"},sub="Tauret", range="Anarchy +2"}
sets.weapons.Dummy = {main="Fettering Blade",sub="Kustawi +1", range="fomalhaut"}
sets.weapons.Last = {main={name="Rostam", bag="Wardrobe 4"},sub={name="Rostam", bag="Wardrobe 3"},range="fomalhaut"}
sets.weapons.Leaden = {main={name="Rostam", bag="Wardrobe 4"},sub="Tauret",range="Death Penalty"}
sets.weapons.Rolls = {main={name="Rostam", bag="Wardrobe 3"}, sub="Tauret", range="Death Penalty"}
In this example you would swap to the dummy mode prior to clear the current equipped weapons.
state.Weapons:options('Rolls','Leaden','Dummy','Savage','Dummy','Aeolian','Dummy','Last','Dummy')
Otherwise you would need to make a third Rostam and use for rolls only. Suspect you would still have issues swapping your other two correctly as they would be in use.