A 6-1 6-2 victory for Keys at Adelaide International 2 gave her a sixth WTA Tour title and a first since a stunning run in 2019 at Cincinnati.
Keys, who faces a tough Australian Open first-round clash against 2020 champion Sofia Kenin, showed her form is coming back after a lean spell.
The former world No.7 has slipped to a lowly No.87 in the rankings, but at the age of 26 she has ample time to climb back towards the top of the game.
This win moves her back into the top 60, with Elina Svitolina and Coco Gauff among the players Keys has fended off this week.
Keys said: "I'm really happy with how today went. There were a couple of opportunities where momentum could have switched, and I think I did a really good job of just regrouping and continuing to focus on my side of the court. Really happy to get a win."
Keys explained her mindset had been "dark" at times in 2021, with her appetite for tennis ebbing away.
She said: "Just knowing from what I was thinking about last year and the deep, dark pit of despair that I put myself into because of that, I don't want to go back to that. I don't want to let myself borderline hate being on the tennis court and hate competing. If I let myself think that way, that's where it goes."
Her motivation is on an upwards curve now, and results like this will help. Keys held serve throughout, did not face a break point, and broke Riske's delivery four times on the way to sealing victory in an hour and six minutes.
Keys added: "I think the biggest takeaway is that things can switch at any moment. As long as you can continue to have the right mindset and keep going for things and keep working hard, things will get better if they're not going well, as long as you just have the right mindset and continue to have a good attitude about it."