Coffee roasted yesterday is not at its best. That is counter to everything the category teaches, and it is the reason a bag bought directly from a roaster sometimes disappoints on the first morning.
Roasted coffee needs a rest before it brews well: about a week for espresso, one to two days for filter. Before that it is carrying too much carbon dioxide, and the gas gets in the way.
The mechanism is the same one behind the bloom. Roasting fills the bean with CO2, which leaves slowly over the following weeks. Brew while a lot of it is still in there and the gas pushes water away from the grounds, so extraction goes uneven. On espresso it shows as bubbles in the flow, an unstable shot and a slightly metallic edge. On filter it shows as a bloom that climbs alarmingly and a cup that tastes hollow in the middle.
Racineux and Tran put the espresso rest at a minimum of a week and name the metallic taste explicitly. Moldvaer's home-roasting guidance runs in the same direction: one to two days for filter, about a week for espresso.
So a roast date is not an instruction to brew immediately. It is a number you calculate from. Freshness is a window that opens a few days after roasting and closes over the following weeks, not a countdown that starts at its best and declines.
What this will not do: waiting will not improve coffee that was poor to begin with, and it will not rescue a bag that has been open in a warm kitchen for a month. It also does not apply to pre-ground coffee, which was degassing on the shelf and has a different problem entirely, measured in hours rather than weeks.
If your new bag tastes metallic, put it away for four days and try again before you conclude anything about the roaster.
