Rovick died in his sleep at a nursing facility in Boise, Idaho, said his wife, Jacqueline.
In 1952, after KTTV acquired a batch of old cartoons and was searching for someone to host a daily cartoon show for children at 5:30 p.m., Rovick came up with a novel idea: Sheriff John.
Rovick knew longtime Los Angeles County Sheriff Gene Biscailuz, "and I had been an honorary Sheriff before I started the show because I was interested in law enforcement work," he told The Times in 2008.
So "I put on a khaki uniform and a badge and got a big white hat, sat at a desk and showed cartoons," Rovick recalled.
"Cartoon Time" with Sheriff John became an immediate hit with young viewers, earning an Emmy Award in 1953 for outstanding children's program.
KTTV by then had added a new show to its schedule at midday, "Sheriff John's Lunch Brigade," which stayed on the air until 1970.
"Come on now, laugh and be happy and the world will laugh with you," he'd sing in a smooth baritone, lip-synching as he entered the door of the sheriff's office set at the beginning of each show. The opening included leading his young viewers in reciting the Pledge of Allegiance.
"We talked a lot about safety, courtesy, manners and things like that," he told the Idaho Statesman in 2005. "We often had firemen or police officers as guests, and I'd warn the kids not to do things like play in the street or get into refrigerators or play with matches."
He'd also do occasional live remotes, taking viewers to see how bread was made, or how cars were assembled at a GM plant in Van Nuys. And, of course, he'd show cartoons (those with Crusader Rabbit were early favorites).
One highlight of the show, whose primary target was 4- and 5-year-olds, was Sheriff John's reading of the names of dozens of viewers who were celebrating birthdays. Then he'd sing "The Birthday Cake Polka" — "Put another candle on my birthday cake. We're gonna bake a birthday cake ..." — as a large cake revolved on a lazy Susan.
Sheriff John also had lunch along with his viewers — he'd usually eat a sandwich and have a glass of milk after saying a brief nondenominational prayer.
"It was a real good little prayer," he recalled in 2008 in The Times, the words still fresh in his mind: "Heavenly father, great and good. We thank thee for our daily food. Bless us even as we pray. Guide and keep us through this day."
Rovick acknowledged that it would be hard to get permission to say grace on a contemporary TV show.
"Oh, they'd fight me tooth and nail today," he said, but at the time no one complained.
"Isn't that amazing?" he said. "That was when everyone was trying to prove that God was dead, and I was out to prove he was still alive, and I won."
From the start, Rovick received encouraging mail from parents, who extended their gratitude for his lessons in manners, safety and patriotism.
"The kids always came first," he said in the 2005 interview. "To some of them, I was a father figure. That was the best thing about being Sheriff John. A lot of those kids loved me."
Rovick once received a letter from a mother saying her young son had asked her how old Sheriff John was. She told him, "I don't really know." To which the boy said: "He must be hundreds of years old. Every day he sings, 'I'm another year old today."
One father wrote a letter of thanks and told him how his young daughter learned to say the Pledge of Allegiance: "... with liberty and justice for all, and now to our first cartoon."
The letters from parents also included one from a mother who said that when a disease took the life of her young son, their pastor read the words to "Laugh and Be Happy" at his funeral.
Sheriff John became an influential TV figure, spawning other law enforcement-type children's TV show hosts around the country.
Rovick was born Oct. 2, 1919, in Dayton, Ohio. While studying speech and dramatics at Michigan State University, he began singing with an eight-piece student band on Saturday afternoons at the student union.
The shows were broadcast by the university radio station and in so doing, he later said, "I got the feeling I liked broadcasting."
He began working occasionally at a local radio station and after graduating in 1941, he landed a job as a staff announcer on a Toledo radio station. But the job was short-lived.
In 1942, Rovick joined the Army Air Forces and flew 50 missions as a radio gunner on a B-25. He was later commissioned a second lieutenant and had temporary duty with the transportation corps on a liberty ship.
After the war, Rovick returned to his old job at the Toledo radio station. Inspired by a colleague who had worked in Los Angeles, Rovick made an audition record and in 1949 drove west.
After KTTV canceled "Lunch Brigade" in 1970 — to "save money," he said in 2008 — Rovick stayed on as a staff announcer until retiring in 1981, after 32 years at KTTV. He then moved to Idaho.
Decades later, Rovick continued to be a welcome sight for those who had grown up with Sheriff John.
"I had a heart attack five years ago," he said in the 2005 Idaho Statesman interview, "and the Boise doctor who saved my life turned out to be a Sheriff John fan. My dentist is a fan, and so are three of the people at the clinic where I get my eyes checked.
"I was walking into a store the other day, and a woman gasped and said, 'Sheriff John!' It just doesn't stop. It's amazing that it's been so many years ago and people still remember the impact the show had on their lives."
Rovick was separated for many years from his wife, Jacqueline, with whom he had two daughters, Wendy Maceri and Sandy Kaiser. They survive him, as do five grandchildren and one great-grandchild.
McLellan is a former Times staff writer.