Ep. 2 Kevin likened Veronica to Madame Satan, Sabrina's Nemesis. Alice Cooper purifies Betty's room from evilness by burning sage after Cheryl was there.Alice Cooper jokes about the Blossoms sacrificing people to pagan gods at their mansion.
Ep. 4 Jughead likened investigation for Jason's murder to Salem Witch Trials.
Ep. 5 Cheryl mentions Greendale.
Ep.7 When Betty is looking for Polly in the attic, you can see an ouija board in a box.
Ep. 8 At the Baby Shower, Grandma Blossom divining Polly's twin children with a pendulum. Alice Copper don't approve her occultism.
Ep. 12 Alice bursting at the Blossoms mansion at the "witching hour of Thornhill"
Ep.13 Betty quoting Macbeth "Something wicked this way comes". Penelope Blossom, mentioning the Grim Reaper and the Sweet Hereafter.
Riverdale # 6 The Stranger (aka The Devil) at Pop's mentioning paying a visit to some women in Greendale. It's implied Pop Tate made a pact with the devil for a successful business year ago.
Not exactly witchy but Jughead and Betty watched A Werewolf in London and in Jughead the Hunger he was a werewolf! Archie also had a werewolf mask in his room and the Bulldogs wore werewolves mask during Archie's audition/hallucination.
Ep 2.01 the "cannibal" Ghoulies, taking the name from the "Groovie Goolies", Sabrina's spin-off.
Ep. 2.02 Donovan - "The Season of the Witch" playing at the end of the episode.
Ep. 2.03 Kevin telling how Midge was "screaming like a banshee".
Ep. 2.05 A portrait of a humanoid goat in Nick St.Clair's hotel room.
Ep. 2.07 The "Mr. American Gothic" man thinking Archie was Jason Blossom because "you never know on the road to Greendale" and the deer soaked in blood headed to Greendale spotted by Archie on the road. Poor Bambi, the witches will party with you lol bonus: Not strictly witchy but Josie singing "Spooky Little Girl Like You"... Eastwick, anyone?
Ep. 2.10 A raven flying and croaking in front of Riverdale High. Baxter High's school football team is called "Baxter High Ravens". Also, Madame Satan has a raven familiar in the comics.
Ep. 2.16 Penelope cultivating "esoteric herbs" in her greenhouse and using Tannis Root to poison Nana Blossom.