For me,
Rollers: 1-3hrs, steady / tempo rides, you can chug a big gear or concentrate on perfecting your spinning but most have little to no resistance, the premium ones do offer this but I’d probably go with cheap rollers and a cheap S/H turbo if I wanted this.
Turbo: Great for harder more intense sessions, anything over 40mins bores me to tears, you can whack up the resistance though so there great for set specific sessions of 30secs on 30 secs off and any variation on the theme, 2x20min tempo/hard is another classic. For me you really need to be dong specific sessions here, you’ll not notice the boredom as you’ll either be going like hell, or recovering, anything else is a waste.