# L2 Rollers
Here we outline how the naive rollup rollers work. This page is only a quick summary - the full documentation of the API is coming soon.
## Overview
The following diagram illustrates the most important parts of the plumbing present in the roller.
We elaborate on the components of this diagram below.
## `%roller-rpc`
The roller communicates with the outside world via a JSON-RPC API, which is implemented with a Gall agent `%roller-rpc`. This is how Bridge communicates with a roller. See the [RPC documentation](https://documenter.getpostman.com/view/16338962/Tzm3nx7x#5a698656-8e7e-433f-9eff-1c6047b9eace) for detailed information on the API.
## `%roller`
`%roller` is the Gall agent which collects layer 2 Azimuth **transactions**, which are a concatenation of an [action](/urbit-id/l2/bytestring.md#actions) and a [signature](/urbit-id/l2/bytestring.md#signatures) and forms them into [batches](/urbit-id/l2/bytestring.md#batch) to be submitted periodically to the Ethereum blockchain.
### Transaction format
See [Bytestring Format](/urbit-id/l2/bytestring.md) for a technical description of how layer 2 transactions are formatted.
### Pending transactions
`%roller` maintains in its state a list of transactions that have been submitted to it since the most recent roll it submitted to Ethereum. These are referred to as **pending transactions**.
### Signing the batch
Each pending transaction already includes a signature from its sender, but the roller itself must also sign the entire batch of transactions with its private key to submit it as a single Ethereum transaction. This signed batch is known as a **roll**.
### Predicted state
Once a roll has been submitted to an Ethereum node, there is a waiting period before a miner includes it in a block.
During this waiting period, the roller applies the submitted batch to the locally held Azimuth state to get a predicted state. This predicted state is presented to the user in Bridge, such as to show which points a given address owns.
### Timer
Each roller may choose to submit rolls on a regular basis, periodically and/or whenever a certain number of pending transactions is reached.
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