The 29-year-old crossed over twice for the Red Rose in last weekend's comfortable victory over Fiji, earning the accolade of man of the match in the process.
Many have questioned Jones's decision to overlook Rokoduguni, including club teammates Matt Garvey and Matt Banahan, but Gustard claims that each call is made on an individual basis depending on the opponent.
"We had a similar situation between South Africa and Fiji," he told Sky Sports News. "There were three or four guys that acquitted themselves very well in the first Test as well - [Mike] Brown and [Jonny] May didn't play the second Test. Rocco didn't play in the first Test on the back of good club form and we have decided to go on a game-to-game basis.
"[We] identify the threats that the opposition will pose, what we need to counter, what we need to defuse, what we need to get right and conversely also what we need to get right in terms of the opportunities we will get from their defensive structures.
"How can we exploit their weaknesses, their frailties? And that's what we've done. So we have chosen a group of players that's staying with us and on the back of that we will get a good 23."
England have won each of their last 12 Test matches, with Argentina and Australia left to come this year.