That's pretty much your own call. While this board is pretty laid back on the subject, I've seen one Amtrak board where some members all but insist to the point of offense if you don't take them up on their plea! LOL!
It certainly wouldn't hurt to price one out, both now and the day before your trip to see if you might want to. As the traveler said, your meals are included, and that would pretty much account for about $60 of the upgrade alone. Add in the horizontal sleeping, your own place to do pretty much as you please without interupting others, and a shower, and the value increases, albeit intangibly.
Keep in mind that you may be able to upgrade once on board at a lower rate - it's one of those risks, but it might be an option. Someone else may well know the minimum roomette cost for that trip - I'd guesstimate it to be in the high one hundreds, but I haven't priced the Sunset in some time.
*** EDIT, on checking the dates of travel, the SL at the time I checked it was $252 for a roomette. Base rate (either through an onboard upgrade if available or if they elect to lower the room rate closer to day of travel) on one would be $184.
Now, if you are absolutely sure you'll be picked up in San Antonio, the rate when I checked it was $207. The base (onboard) rate was just $137. That would probably be in the "worth it" category to me for a 29 hour trip, but it's your call.
Keep in mind, there is no problem in changing your reservation to actually end in San Antonio. Amtrak can typically make such changes on the fly if you haven't picked up your tickets yet, and the ticket counter can usually make exchanges if you have the ticket in hand already printed.
