Rollers in the morning, Trainer in the evening

They really serve two different purposes.

If you want to just spin around or do a lighter workout, rollers fit that task. Also you can do longer intervals on rollers since your wattage won't be as high.

If you want to do maximal intervals, definitely the trainer. This is your 30s-5min intervals.

I would start out getting a trainer (look for deals now since the winter is over for most places) since its easier to do group indoor training with a trainer. Then next year look for rollers. If you buy quality equipment, it'll last for a long time (especially rollers) so think of it as a longterm investment in your cycling.