This is an interesting topic and I've read NEARLY every single post so here's my 2cents because there were plenty of instances where non-magical items needed a RR in our campaigns.
My understanding was that the item level was the same as the "creator's level."
A level 5 blacksmith makes a non-magical sword = level 5 sword. Could he make a really crappy level 1 sword? Sure, but why would he? It's not good for business. "Don't go Dingledong the Smithy. All of his swords break after a week of use." Can a level 5 blacksmith make a level 10 sword? No. How could he possibly?
Higher quality requires higher skill, higher skills (should) inherently impart higher quality. As a default, we always gave our non-magical items level 5 for RR. Any Average-Joe adventurer could afford the base level (level 5) equipment and a decent apprentice with a smithy should be outputting at least decent grade items. The Smith's reputation in on the line again. If the item had +5, +10, etc for quality, not magical, we gave the +5, +10 bonus to the item's roll for Breakage Factor when needed.
Elemental material items (from Elemental Companion - RM2) gave base level elemental forges required to manipulate elemental material, the base skills required, and those items had inherently higher final product levels; Level 10+ due to the amount of skill needed just to manipulate/use the stuff (Mithril, Eog, Laen, Cotoetine, etc.). As the material was already magical, it automatically received RRs.
Items that were later imbued with magical properties AFTER creation still defaulted to the item quality. However, I think* there were minimum requirements on the item in order for the imbuing process to work. Ex.: Level 9 spell property, needs at least level 9 item to accept the property and the spell caster/alchemist had to be at least level 9 in order to cast that spell, etc. So that too, gave an inherent RR = level 9. Why would someone waste time/effort/money/resources to put a level 9 spell into a level 1 item?
All of that being said, I (and the other players/GMs from my group) agree with Warl:
"My understanding is that it gets No RR on it's Own, Unless it has an Enchanted nature."
It seemed to work out OK for because by the time they ran into an evil-doer who could cast those spells, the PCs were already stronger, smarter, and better equipped with hopefully magical items. If they are fighting a level 8 spell caster, casting a level 8 spell, they have 3 rounds to try to disrupt his spell. It all balanced out.