The Power of As if
"As if" is more than just a 90's cool girl expression, it is actually the key to understanding how stored spells work.
To store a spell in the Ring (and the stone uses similar language):
This ring stores spells cast into it, holding them until the attuned wearer uses them...Any creature can cast a spell of 1st through 5th level into the ring by touching the ring as the spell is cast. The spell has no effect, other than to be stored in the ring.
Notice that there is no reduction in the requirements for casting the spell when storing it. The ring "stores spells cast into it", cast as normal, with all components and other requirements, but with the additional requirements of touching and being attuned to the ring, and the additional consequence of the spell not having any effect other than being stored.
In order to use the ring, you must be attuned to it - but unlike some magic items, there is no class requirement for attuning. Even creatures without the Spellcasting ability can cast spells from the ring, which is our first clue as to what "as if" means - the requirements of the stored spell are met by the power of the ring, not the caster.
Thus when releasing a spell, the casting requirements are greatly altered (emphases mine):
While wearing this ring, you can cast any spell stored in it. The spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster, but is otherwise treated as if you cast the spell. The spell cast from the ring is no longer stored in it, freeing up space.
It is not that 'the original caster supplies the DC etc. but you must supply the rest'. Rather, it is that 'the original caster supplies the DC etc. and you get to act as if you had supplied the rest.' What it is saying is that the ring will take the place of any spell requirements at the time of casting. You do cast the spell from the ring as if you actually could cast, or as if you were actually casting the spell - all components are part of the "otherwise" conditions supplied by the stored spell.
If the spell has component requirements, whether verbal, somatic, or material (expended or not), the power stored by the original casting of the spell (which did meet these requirements) allows you to now cast the spell as if the requirements had been met in this casting. They weren't actually met in this casting, but you are allowed to cast as if they were.