diff --git a/tests/io/test_asn.py b/tests/io/test_asn.py
index 8369083a..dc7c6a20 100644
--- a/tests/io/test_asn.py
+++ b/tests/io/test_asn.py
@@ -2,6 +2,7 @@
 import threading
 import time
 
+import h5py
 import numpy as np
 import zmq
 
@@ -162,6 +163,30 @@ def get_socket(self, address):
         return socket
 
 
+def test_read_handles_exclusive_roi_end(tmp_path):
+    path = tmp_path / "sample_asn.hdf5"
+    with h5py.File(path, "w") as file:
+        header = file.create_group("header")
+        header["time"] = 0.0
+        header["dt"] = 0.1
+        header["dx"] = 10.0
+
+        file.create_dataset("data", data=np.zeros((4, 4), dtype=np.float32))
+
+        cable_spec = file.create_group("cableSpec")
+        cable_spec["sensorDistances"] = np.array([0.0, 10.0, 20.0, 30.0])
+
+        demod_spec = file.create_group("demodSpec")
+        demod_spec["roiStart"] = np.array([0])
+        demod_spec["roiEnd"] = np.array([4])
+
+    da = xd.open_dataarray(path, engine="asn")
+
+    assert da.shape == (4, 4)
+    assert da["distance"][0].values == 0.0
+    assert da["distance"][-1].values == 30.0
+
+
 class TestZMQSubscriber:
     def test_one_chunk(self):
         address = get_free_local_address()
diff --git a/xdas/core/routines.py b/xdas/core/routines.py
index 587c955e..aea4f60b 100644
--- a/xdas/core/routines.py
+++ b/xdas/core/routines.py
@@ -342,14 +342,23 @@ def open_mfdataarray(
         else:
             iterator = as_completed(futures_to_paths)
         objs = []
+        failures = []
         for future in iterator:
             try:
                 obj = future.result()
             except Exception as e:
                 path = futures_to_paths[future]
+                failures.append((path, e))
                 warnings.warn(f"could not open {path}: {e}", RuntimeWarning)
             else:
                 objs.append(obj)
+    if len(objs) == 0:
+        if failures:
+            path, error = failures[0]
+            raise RuntimeError(
+                f"could not open any file with engine={engine!r}; first failure was {path}: {error}"
+            ) from error
+        raise FileNotFoundError("no file to open")
     return combine_by_coords(objs, dim, tolerance, squeeze, None, verbose)
 
 
diff --git a/xdas/io/asn.py b/xdas/io/asn.py
index e1a32530..b4e008f9 100644
--- a/xdas/io/asn.py
+++ b/xdas/io/asn.py
@@ -1,5 +1,5 @@
 import json
-from bisect import bisect_left
+from bisect import bisect_left, bisect_right
 
 import h5py
 import numpy as np
@@ -11,6 +11,18 @@
 from .core import parse_ctype
 
 
+def _get_roi_bound_indices(all_dists, n_start, n_end, dx):
+    start_index = bisect_left(all_dists, n_start * dx)
+    if start_index >= len(all_dists):
+        raise IndexError("ROI start lies beyond available sensor distances")
+
+    end_index = bisect_right(all_dists, n_end * dx) - 1
+    if end_index < 0:
+        raise IndexError("ROI end lies before available sensor distances")
+
+    return start_index, end_index
+
+
 def read(fname, ctype=None):
     ctype = parse_ctype(ctype)
     with h5py.File(fname, "r") as file:
@@ -33,17 +45,19 @@ def read(fname, ctype=None):
 
         # Loop over ROIs, get the start/stop index before downsampling
         for n_start, n_end in zip(demod["roiStart"], demod["roiEnd"]):
+            # ASN stores ROI end as an upper boundary. Use the last sampled distance
+            # that does not exceed that boundary instead of indexing the insertion point.
+            i_start, i_end = _get_roi_bound_indices(all_dists, n_start, n_end, dx)
+
             # Get the index where the ROI starts based on the position in the
             # distance vector. This solves the issue of rounding during decimation
-            i = bisect_left(all_dists, n_start * dx)
             # Append the data index and optical distance to the buffers
-            dist_tie_inds.append(i)
-            dist_tie_vals.append(float(all_dists[i]))
+            dist_tie_inds.append(i_start)
+            dist_tie_vals.append(float(all_dists[i_start]))
 
             # Repeat the procedure for the index/distance at which the ROI ends.
-            i = bisect_left(all_dists, n_end * dx)
-            dist_tie_inds.append(i)
-            dist_tie_vals.append(float(all_dists[i]))
+            dist_tie_inds.append(i_end)
+            dist_tie_vals.append(float(all_dists[i_end]))
 
     nt = data.shape[0]
     time = Coordinate[ctype["time"]].from_block(t0, nt, dt, dim="time")