Simple question. Can these two character classes be created at party creation with a high enough role, or are they only possible through class changing?

First, it's "roll", not "role".

Second, as for the answers:
* Samurai can be created at the start, but you need to be lucky. (I think Dwarves, Elves and Gnomes are the best options; Hobbits focus too much on Luck which isn't needed to become a Samurai, and Humans are actually rather lousy due to their low Piety and no advantage to compensate. Note that race only matters in the long run if you are playing the SFC/SNES version.)
* Lords, I believe, can't be created in most versions, though you can start with one by importing one from an earlier Wizardry game (if you're playing the Apple 2 version, you can use Wizardry 1's identify glitch to get one; your level and stats will go back down on transfer, so you won't be breaking Wizardry 5 by doing this). It *might* be possible in the SFC/SNES version, provided you get incredibly lucky, but don't count on it.

Also, don't worry about the aging from class changing; it's easier to reverse aging in this game than in any other Wizardry with this mechanic.

Both can be created at creation. Unless I'm confusing with another game only the Ninja is excluded, needing 17 in all stats.

I looked over the manual and it looks like Lords can't. If if is possible to create one, it would require a very high roll.

I'm super late posting this, I know. Sorry for the necro, but just for anyone for future reference:
The highest bonus roll you can get in Wizardry 5 is 60. Yes, 60 bonus points. It is super rare, but if you get it, you could even make a ninja at character creation.

Is this true in all versions?

Remember that the SFC/SNES version does have a few differences, most notably being the way attribute caps are handled. For example, in computer versions (and also the PSX version), if you somehow rolled a Hobbit with 60 bonus points, the game would softlock, as there'd be no way to spend them all; 58 points are enough to get 18s in all attributes, which is the cap in most versions. Also, a Human needs 62 bonus points to start with all 18s. (Why are Humans so terrible in the earlier Wizardry games? No really good stats, one really bad stat (Piety), and the worst stat sum of all the races. At least Wizardry 8 finally fixed Humans to make them worthwhile.)

Hm, I'm not 100% positive on that. I do know for a fact that it is true for the SNES version. When the CRPG Addict played Wiz 5 on his blog he managed to roll a 43 during his character creation- and this was on the DOS version.

It is possible that the DOS version (and other versions that are sufficiently similar) might cap the bonus points by race, with humans capped at 62 and hobbits at 58, in order to prevent situations like that softlock from occurring. (With that said, however, the softlock isn't particularly serious, as I believe the game auto-saves when you enter the training grounds and after every operation there, so all you would end up losing is the stat roll that caused the softlock.)

By the wa, if you actually want to attempt to create a Lord or Ninja, your best chance of creating one is to use a Hobbit, as their higher luck results in fewer bonus points needed (note that they're the worst choice if you're just trying to make a Samurai, however).

Be aware that, in the SFC/SNES version (but not other versions), such a character won't be as good in the long run as a Gnome, as Gnomes get better STR and VIT while still having enough AGI to (nearly?) always act before the enemies and (i believe) avoid randomly triggering traps when trying to disarm them; with that said, for Ninjas (but not Thieves) 22 AGI (which only a Hobbit can get) will increase the chance of successfully inspecting a trap (but note that CALFO exists). Also, note that what I wrote in this paragraph does not apply to other versions of the game, as other versions don't cap stats based on race.