Games like Roundguard
Games like Roundguard include Peggle Deluxe, Hades, The Binding of Isaac: Rebirth, Vampire Survivors, and Peglin. We matched them by the tags players give Roundguard on Steam (Pinball, Physics, Puzzle, Cartoon, and Roguelike): closest matches first, and among equally close ones the better-known games.

Peggle Deluxe
Shared: Puzzle · Physics · Arcade

Hades
Shared: Roguelite · Roguelike · Action Roguelike

The Binding of Isaac: Rebirth
Shared: Roguelike · Dungeon Crawler · Action Roguelike

Vampire Survivors
Shared: Roguelite · Roguelike · Action Roguelike

Peglin
Shared: Pinball · Roguelike · Roguelite

Noita
Shared: Physics · Roguelike · Dungeon Crawler

How Many Dudes? The Roguelike Autobattler
Shared: Roguelike · Singleplayer · Dungeon Crawler

RACCOIN: Coin Pusher Roguelike
Shared: Roguelike · Singleplayer · Strategy

Darkest Dungeon®
Shared: Dungeon Crawler · Roguelike · Singleplayer

Slay the Spire
Shared: Roguelike · Singleplayer · Roguelite

Megabonk
Shared: Roguelike · Roguelite · Action Roguelike

Zuma Deluxe
Shared: Puzzle · Arcade · Physics

Brotato
Shared: Roguelike · Singleplayer · Action Roguelike

Ballionaire
Shared: Roguelike · Pinball · Singleplayer

Hades II
Shared: Roguelike · Roguelite · Dungeon Crawler

Poly Bridge
Shared: Physics · Puzzle · Singleplayer

Zup! S
Shared: Puzzle · Physics · Singleplayer

Balatro
Shared: Roguelike · Singleplayer · Roguelite

Donut County
Shared: Puzzle · Physics · Casual

Moonlighter
Shared: Roguelike · Dungeon Crawler · Roguelite

Stoneshard
Shared: Roguelike · RPG · Dungeon Crawler

The Binding of Isaac
Shared: Roguelike · Action Roguelike · Procedural Generation

Sol Cesto
Shared: Puzzle · Roguelike · Dungeon Crawler

Dungeon Clawler
Shared: Arcade · Physics · Roguelite