2. Roby showed he can bury threes last season
It wasn't on a high volume, but Isaiah Roby was very effective from beyond the arc last season. He made 44 of his 99 attempts for a 44.4% mark. For comparison, Josh Richardson's 40-of-90 in San Antonio last season was the same percentage.
I don't imagine the Spurs will need Roby to take many threes when he's on the court, but just the ability to knock down that shot should help spread the floor more than more traditional bigs like Jakob Poeltl.
Last March, Roby shot 4-of-5 from downtown on two separate occasions, scoring 30 and 26 points in those contests. It's clear he has a nice outside shot, and that's a quality that's increasingly beneficial with each passing NBA season.
Given his length, it's difficult to block Roby's shot, so when he's on, he can be a real offensive asset for a team that will likely be on the bottom five of NBA offenses next season. The Spurs weren't impressive in 3-point accuracy (35.2%, 18th) or 3-point attempts (32.0, 25th) last season, so Roby could help in that department.