On the Merits of Roll-in-Order
I've never been a fan of 'roll stats, then assign them in any order'. To me, that only adds the worst type of randomness.
Randomness during character creation comes in two flavors - making characters more varied, or making them more powerful.
For a simple example: imagine during character creation, you rolled on a table to get a random unique power. That's interesting; it makes characters different. Powers might be overall more or less useful of course, but hopefully they are close enough in utility/power that all options are something interesting to have.
Contrast the idea of a point-buy system where you roll for how many points you get. That rarely adds anything interesting to the game; some players will simply be more fortunate than others with no counterpoint.
Rolling stats then assigning them however you want is closer to the latter than anything else. If your idea is to play a fighter, you'll assign the stats in str-con-dex-wis-int-cha order (or whatever order fits your concept), and the only thing the dice are doing is determining how strong or weak your character is.
In a roll-in-order system, characters might end with unusual combinations of stats. If you have high INT and CHA, you might make an unusually charismatic wizard, while high DEX and WIS might make a dextrous cleric or a very wise thief (or, of course, you can ignore your high stats and play an even more unusual concept).
This means roll-in-order actually makes more varied, interesting characters, that you might not play otherwise, instead of simply playing the same cookie-cutter characters over and over, with the only different being whether you've managed 14 or 15 strength this time.
All that said, I am sympathetic to the idea that someone who really wants to play a magic-user ought to be able to play a magic-user.
For that, I like the idea of allowing the player one stat swap - for example, swapping STR for INT. This might be a universal bonus, or something unique to humans.