After a Factory Reset you will NOT be able to set up your Roku without a working physical remote. The Roku app on a phone or tablet cannot communicate with the Roku until the Roku has been connected to your local network, so you can't use the Roku app to establish the net connection.
All means of setting up without a physical remote require knowledge of a prior network to which the Roku is still attempting to connect. . Without this knowledge your only recourse is to use a physical remote.
But to answer your direct question, yes, you can do a factory reset. This wipes the Roku's memory and returns it to a just-out-of-the-box state. After a factory reset you'll be setting the Roku up all over again from scratch, including setting up your net connection, linking to your Roku account, adding your channels, and logging back into any channels whose subscriptions require logins.
With no working remote you can perform a factory reset by pressing the reset button on the device and holding it for a minimum of 30 seconds (no matter what you may see on the screen during this period).
With a working remote you can perform a factory reset via Roku menu path Settings > System > Advanced system settings > Factory reset.
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