I quoted the entire text on spell storing from SRD.PDF below.
Part 1 - is the spell cast from the ring a "spell"? I [humbly] agree with Thanee. The ring is *activated*, as it says in this sentence here: [The activation time for the ring is same as the casting time for the relevant spell, with a minimum of 1 standard action.] Once you agree that the spell inside the ring is activated, NOT cast, a lot of stuff falls into place. You don't need any spellcasting ability like you might with a Wand, you don't need to make Concentration checks, etc, etc.
Part 2 - Can you metamagic a spell with a Rod, before you put it into the ring? This is a little less clear. These 2 sentences [Metamagic versions of spells take up storage space equal to their spell level modified by the metamagic feat.] and [A spellcaster can use a scroll to put a spell into the minor ring of spell storing.] would have me believe that a caster could use items to place the spell into the ring. If you can use items, you should be able to use Rods, too.
Of course, as a player, I would totally understand a DM taking the "hard line" regarding part 2 - Not allowing the combining of the power of the Ring and a metamagic Rod. It's Very Powerful.
On a side note, storing a Quickened Spell (even if you have to add the +4 levels) doesn't seem worth it - since the Ring still requires an activation time of 1 standard action. Or did I miss something?
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Spell Storing, Minor: A minor ring of spell storing contains up to three levels of spells that the wearer can cast. Each spell has a caster level equal to the minimum level needed to cast that spell. The user need not provide any material components or focus, or pay an XP cost to cast the spell, and there is no arcane spell failure chance for wearing armor (because the ring wearer need not gesture). The activation time for the ring is same as the casting time for the relevant spell, with a minimum of 1 standard action.
For a randomly generated ring, treat it as a scroll to determine what spells are stored in it. If you roll a spell that would put the ring over the three-level limit, ignore that roll; the ring has no more spells in it. (Not every newly discovered ring need be fully charged.)
A spellcaster can cast any spells into the ring, so long as the total spell levels do not add up to more than three. Metamagic versions of spells take up storage space equal to their spell level modified by the metamagic feat. A spellcaster can use a scroll to put a spell into the minor ring of spell storing. The ring magically imparts to the wearer the names of all spells currently stored