It doesn't really avoid curves, though, even when carved into stone. Look at the inscription on Trajan's Column [1], f'rinstance; yes, it's got the classic U written as V, but the C, D, O, S etc are all as curvy as you could possibly want.

The Romans wrote most ephemeral stuff on wax tablets which could be smoothed over for re-use; this is where the phrase "tabula rasa" comes from. Some examples survive and also show curves [2].

[1] https://upload.wikimedia.org/wikipedia/commons/b/b8/002_Conr...

[2] http://www.ancient-origins.net/news-history-archaeology/newl...