There are three types of magical items in Ə (so far). We've seen complementary magic items like Wands and Staves that provide their power in conjunction with spell casting, or magic weapons that provide a boost to combat. We've also seen innate magic items where their power is either always "on", such as Boots of Joyous Comfort, or activated, such as the Potion of Tasty Numminess which must be consumed to receive any benefit.
The third type is powered magic items, where the user needs to provide magical power (roll the Sorcerer die) to access the item's, uh, power. (Don't you hate it when your lexicon is larger than your vocabulary?) A limited example is the magic scroll. Unlike a magical scroll, where the amount of magic that is put into the casting is only of concern to determine if the spell is triggered, most powered magic items depend on Degree of Success, like magical spells. (Although, it could be argued that casting a spell from a scroll isn't an act of providing magical energy but is instead a check on the character's ability to read the scriber's handwriting, much like a nurse needs to be able to decipher a doctor's illegible chicken scratch.) Also unlike scrolls, most magic items aren't consumed by the magical energies used to form the magical effect. In general, powered magic items are usable by anyone, but items requiring a minimum Sorcerer Rank are not unknown (even if I haven't thought of any, yet).