Archer said:
The ring only lets you control 12 HD worth of animals while you wear it. It is not the same as casting the spell.
From the SRD:
Animal Friendship
On command, this ring affects an animal as if the wearer had cast animal friendship. The ring wearer can befriend 12 HD worth of animals (see the spell description). If animal friendship is already on the character’s spell list, this ring allows the character to befriend additional animals.
I don't see any mention of the effect being dependent on wearing the ring at all. In fact, it specifically says it affects an animal as if the wearer had cast the spell
Animal Friendship, the effects of which are instantaneous, and lasting.
Casting the spell from a scroll is the same as casting it yourself. You can only use a scroll with use magic device or having the spell on your spell list.
Actually, no. Again from the SRD:
For potions, scrolls, and wands, the creator can set the caster level of the item at any number high enough to cast the stored spell and not higher than her own caster level.
A wizard can choose to lower the caster level on a scroll he scribes (so long as the caster level is at least as high as the minimum required to cast the spell) to reduce the cost. In such a case, the effects of the spell, when activated from the scroll, would be less than had he cast the spell himself (since his actual caster level would be higher than the scroll's.)
For example, a 10th-level wizard could scribe a scroll of
Fireball at caster level 5. The scroll, when activated, would discharge a 5d6 fireball, even though the wizard himself is capable of casting
Fireball and dealing 10d6 damage.
Likewise, a low-level wizard can buy a scroll of a spell he has access to, only at a higher caster level than himself. He'd have to succeed at a caster level check to activate the scroll without a mishap, but the effect would be greater.
For example, a 5th-level wizard could purchase a scroll of
Fireball at caster level 10. The scroll, when activated, would discharge a 10d6 fireball (if he succeeds at his caster level check,) even though the wizard himself is only capable of casting
Fireball and dealing 5d6 damage.
The question about
Animal Friendship is a tricky one. The Ranger ability list clearly defines the limits of the class ability, but it doesn't address what happens if the ranger casts the spell from a scroll scribed by a higher level ranger or druid.
Consider also the rogue. He can use the Use Magic Device skill to activate a scroll of
Animal Friendship as well and, from a rules standpoint, gain as many HD of animal companions as the caster level (if a druid scroll) or half the caster level (if a ranger scroll) of the scroll.