Rooted Android device and more regular updates?

Generally, if you're talking about updates for any ROM, then you should know that it doesn't matter if you're rooted or not to get regular updates.

Moreover, rooting modifies your /system partition, due to which OTAs (for stock ROM) will fail to install, because nowadays most updates are Block-based OTAs.

So, for successfully installing official OTAs, it's better not to root your phone or use systemless root.

You're not getting regular updates because maybe Samsung hasn't yet released any updates for your device.

But if your phone is rooted and if you have flashed a custom recovery, then, as you said, you can install any custom ROMs with active developers which might be getting regular updates.

As @Tamoghna said, you can install ROMs like CyanogenMod which might provide daily updates.

You can also check for CM daily updates using apps like CyanDelta Updater (as said by @Firelord) which provides delta updates of minimal size.