For train travel from Rome Termini to Monterosso on a Monday in late September, is it advisable to pre-book train? 2 adults with luggage ( hopefully on light,manageable side:)...and then on a Thursday from Monterosso to either Florence or Pisa?
da,
For travel on the Rome - Cinque Terre route, I'd recommend using one of the direct trains from Roma Termini to La Spezia Centrale. There are several of those each day and it's the best method as travel time is only about 3H:45M. From La Spezia you'll transfer to the Regionale train to Monterosso (a short journey).
If you're willing to commit to a specific train, date and departure time, you can save considerably by pre-booking. The cheapest tickets are non-refundable and non-changeable, so choose carefully. The luggage isn't a factor when purchasing tickets, but packing lights is always prudent as you'll be lifting it on and off the train!
For the segment from La Spezia to Monterosso, I'd suggest purchasing that ticket at a Kiosk at Roma Termini, and then just validating prior to boarding the train in La Spezia (DON'T forget to validate!).
Check the Trenitalia website for times and other details on the direct trains. For purchasing tickets, you might try www.capitainetrain.com as their website is more user friendly than Trenitalia.
If you book now, you could get it for 11.70 euro per person on the IC train to La Spezia with a Regionale connection to Monterosso. Last minute it will cost 46.20 euro.
Monterosso to Pisa or Florence can be done with all Regionale trains, so no reason to buy ahead.