Depends upon your game's setting, its intended audience, and the intended deployment platforms.
The first roguelikes were mostly played on old green screen terminals which had either 40 or 80 character width and 25 lines for the most part. Working that out to modern terms, assuming 4:3 aspect ratio of the terminals, you were looking at something like 8x16 or 8x12 fonts. A bit later on 640x480 monitors, square sizes became a favorite for many with 8x8 fonts giving a nice sized map onscreen.
We're in an entirely different world today. It used to be considered rather expensive, even prohibitively expensive, to have a scrolling map or player character-centric view (expensive in memory, cycles, and bandwidth). These days I believe the resolution of the intended deployment platform is the primary driving criteria. It even influences what kind of playable game you can reasonably expect to provide. For instance, a game with primarily ranged combat is going to be difficult to do justice to on an smart phone display.
A common 'mistake' that has been made was to assume that larger screens and higher resolutions meant you could make things smaller and fit more stuff on the screen. Well... that's true to a point, but only to a point. The larger the screen is, the more I find myself viewing from a further distance, and vice versa. This offsets the screen size and resolution aspects a bit.
Rather than try to give you a straight up answer, I'll simply say, look at the tile based games you think look good on youtube reviews and choose that same number of cells horizontally and vertically. Scale your fonts and/or tiles to match. Note that this will have a profound effect though on what type of game you can present effectively. As a rule of thumb, the lower the size of the viewport (in cells), the more you want to emphasize short range attacks and indoor environments.
One way of getting more bang for your buck out of a given viewport size is to make your game have a player centric viewpoint, where you are showing only the 'awareness zone' of the player's character on screen. You could go even further and use a rotating display and model awareness as a conical volume. I played around a bit with that idea in my Snapshot prototype
https://love2d.org/forums/viewtopic.php?f=5&p=113183 but wasn't satisfied with the results*.
A somewhat odd side effect of all this is that having a large number of cells displayed on the screen actually reduces the amount of time you'll have to spend on graphics - since the detail is lower - even to the point where using completely abstract symbols makes for a clearer more understandable display than any image you could come up with (or reinvent ascii fonts). Conversely the fewer cells you display on screen, the more important each becomes and you'll spend more and more of your time working on the graphics and less and less on the game behind the screen. Which... is what roguelikes were all about up until the last decade or two.
*Also some research indicated that rotating views could make some people physically ill --- oops.
