I have made and used the roller bucket trap having chicken feed around my barn and it worked great. Rats are very intelligent though and after a few of them bite it the others will learn to avoid it.
Some trappers suggest disabling the trap periodically, like every week, and letting the rats feed without trapping them for a week.
One week trapping and one week feeding ... repeat
Others suggest making or buying a different trap and feeding them for several days before enabling the trap.
This keeps them off guard and stimulates them to investigate. Setting several traps in different places can fake them out.
Have you tried this?