Standard Red Romas Red Roma tomatoes usually grow to about 4 feet, or 48 inches, tall. Not all varieties are limited to this size, however. San Marzano tomato plants can grow up to 62 inches high, or a little over 5 feet, and produce large crops of early fruit.Click to see full answer. Hereof, how big are Roma tomatoes? about 3 inches Also Know, do Roma tomato plants need to be staked? All tomatoes need plenty of water, soil rich in organic material and need to be staked up off the ground for the best fruit production. Roma tomatoes are no different. Once your roma tomato plants are 6-12 inches high, start staking the roma tomatoes up off the ground. Similarly, how much space does a Roma tomato plant need? Growing Roma Tomatoes Romas need the same conditions as other tomatoes—well-drained soil high in organic matter, full sun, and plenty of water. Plant them about 14 to 20 inches apart. They’ll be ready to harvest in about 75 to 80 days.Why are my Roma tomatoes so small?The most common cause for small tomatoes is stressed plants. The soil should be kept consistently moist or the plants may show signs of stress such as wilting, leaf drop or tomatoes that are too small. Many gardeners grow tomatoes in self-watering containers to ensure proper soil moisture for fruit development.