The pair are already parents to 3-year-old daughter Emerson and 1-year-old son Brooks.
After being on "baby watch" the night before, Tolbert posted that their son was born at 5:33 a.m.
"Mama and Baby Boy doing great!" he simply captioned an Instagram Story.
Their new bundle of joy joins the parents' two other children. Roper gave birth to her and Tolbert's first child, daughter Emerson, in August 2017. They welcomed their second child, son Brooks, in July 2019.
Roper also posted a photo of her and Reed, writing, "He's here and he's perfect."
On Monday, the couple shared gorgeous new portraits of Reed on social media.
One image showed the cutie and a teddy bear lying on a blue blanket printed with his name.
"We welcomed him earth side to our family on November 14, 2020 at 5:33am at home. Born with a head full of dark hair and blue eyes," Roper captioned the photo.
She also posted a video on her Instagram Stories, showing the newborn. "Everybody say hello to Reed," she said as he peacefully slept.
Another adorable photo showed Emerson holding her new little brother. Brooks was meanwhile snapped on his tip-toes trying to peek into Reed's basinet.
"Brooks is super curious, but we've had to keep him mostly downstairs the past couple of days because he doesn't understand gentle touch yet," she explained, before asking her followers for advice.
Tolbert meanwhile posted a sweet pic of Reed sleeping in a cute white outfit. "It’s official! Say hello to Reed Harrison Tolbert. He was born on 11/14/2020 at 5:33 AM. Weighing in at 8 pounds 4 ounces and 21 inches long," he wrote.
Roper and Tolbert, both 33, announced they were expecting in May. Days later, they opened up to ET about their expanding family, with Roper admitting she had some "anxiety" about giving birth again. The Bachelor alum unexpectedly gave birth to Brooks in her closet.
"At [Brooks'] birth I definitely dealt with what I considered was trauma," Roper said. "So it's something that I am trying to be mindful of this pregnancy, just to check in with myself, and validate myself, and just be in a good mind frame. I just want to be prepared for whatever may come this time around."
While learning baby No. 3 was on the way was a big shock to the couple, they were "so excited and happy" to be growing their family.
"Sometimes things come in waves that you don't plan, but those are the best surprises," Roper said.
As for future family plans, Tolbert said he had a "strong feeling that this will be our last [child]." "Never say never of course, as we have learned," he joked.
"When we first got married, we put it out in the universe that we wanted four children, so who knows," Roper added. "This might be totally out of our control. But I think three is a really good number."
See more on the couple in the video below.