I think "kuroga" can be used as infinitive and gerund or noun:
Ufagio unaoegemea kitanda huruhusu roho waovu kwenye ufagio huo kuroga kitanda hicho
• A broom against a bed allows evil spirits in the broom to cast a spell on the bed
Je, inahusisha kuroga au kulinda mtu asirogwe?
• Does it involve the casting of or protection from spells?
(Here, "kuroga" would be "spells")
From Glosbe: https://glosbe.com/sw/en/kuroga
A Swahili song uses the word "Niroge" (this would be translated as "Bewitch me"/"Cast a spell on me"):
https://www.youtube.com/watch?v=rjaNNV-cih8 (Vanessa Mdee - Niroge - w/lyrics)
" Roga" is looking like the verb, and "kuroga" noun in plural. But " roga" has also meaning - enchant, jinx.