This will be my 1st post on Websleuths though I have been reading it for a while. My primary case of interest is the Morgan Nick abduction from Alma, Arkansas in 1995. Having said that, I do want to post my analysis of this case based on the information put forth and what seems to be the most likely explanation from the behaviors we know about.
Roger came to school on the school bus as was apparently his normal pattern. He did what was normal for him and went into the school and and to his locker upon arrival. From what we know, this is the last time he was accounted for at school. He did not attend any classes. We have no reports of any struggle or strange events from the school. The most logical explanation at this point seems to me to indicate that Roger planned to not remain at school that day. As someone who has worked at schools for 30 years, skipping is usually tied to one of a handful of choices. Parties (Get togethers), girlfriend/boyfriend, work, or personal demons. It is also almost always the case that the truant student is not doing it without other students (or persons) knowing it unless it is personal demons.
As a school official (and I would think, LE) the 1st thing we look for are others who are absent on that day and close friends who were not absent on that day. I do not think we can say at this point WHY Roger left, but based on what we know, I think he intended to come back to school before the day was over. We know this because he took no extra money nor clothes and had (as far as I know) no other way home after school than the bus. My best guess is that Roger willingly left to meet someone or deal with some issue, fully intending to return to school that day, but for whatever reason, did not. The WHY can likely tell us WHO and finally let us know WHAT happened to Roger.
I believe the best angle still available for investigators is to interview Roger's friends and associates. Focus needs to be placed on faculty and staff who were not at school either some or all the time that day or who were absent the following day. It is conceivable that the tragedy might not have occurred until after school hours and the next day would have been a time for cover-up and regrouping.