Can spells from the Ritual Caster feat be cast using spell slots?

Question

I am a 4th-level Fighter (Eldritch Knight). I can choose to take a feat. I am interested in the Ritual Caster feat.

If I learn the Ritual Caster feat, could I later cast the spells learned from the feat with it using a higher-level spell slot?

Answer 1

You can't use Spell Slots from your class to cast spells you know from Ritual Caster

From the description of the Ritual Caster feat:

You have learned a number of spells that you can cast as rituals.

Aside from that, nowhere does it say that you can cast them as usual spells using spell slots from your class. To be clear, remember that casting a spell as a ritual explicitly doesn't spend spell slots, and doesn't allow you to cast it as a higher level either.

Certain spells have a special tag: ritual. Such a spell can be cast following the normal rules for spellcasting, or the spell can be cast as a ritual. The ritual version of a spell takes 10 minutes longer to cast than normal. It also doesn't expend a spell slot, which means the ritual version of a spell can't be cast at a higher level.

As an example of clearly stating when you can use your Spellcasting spell slots for other spells, when you multiclass into Warlock it's explicitly stated in the rules on multiclassing:

If you have both the spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the spellcasting class feature, and you can use the spell slots you gain from the spellcasting class feature to cast warlock spells you know.

It should be assumed that, if it was intended that spells from Ritual Caster could be cast (as normal spells) using spell slots from the Spellcasting feature, it would say so, similar to this text.

Answer 2

No

PHB 169, the Ritual Caster feat, says (emphasis mine):

You have learned a number of spells that you can cast as rituals.

So, you can't cast a ritual from the book as a normal spell, because they must be cast as rituals.

PHB 202, under Rituals (from the previous page; emphasis mine):

It also doesn't expend a spell slot, which means the ritual version of a spell can't be cast at a higher level.

You can't cast a ritual as a higher level spell by using a higher level spell slot, because they don't use spell slots at all.